ES-SX-350X Carb rebuild Tutoral

[Flyingw]

I told AF79 I would assemble an instruction for rebuilding the ES/SX/350X carbs so as I put this information together, I will do it here. This will benefit everyone who wants to do the work their selves. Right now I'm out of ES/SX carbs to use as illustrations so I will be using a 350X carb for this purpose. I have fours carbs inbound and hopefully at least one of them will show up before I finish with this instruction. In any case, when one does show up, I will post illustrations.

Please do not post to this thread until I say so. I want it to flow without posts in-between. When I do get it finished then by all means post away but for now just standby.

[Flyingw]

First of all, lets look at the differences between the 85 and 86 rebuild kits. I have use a few different kits over the years and they are all basically the same but lately I've been buying Shindy kits from RJATV on Ebay. About $18.00.

1985 Kit Inventory

Bowl Gasket
Top Plate Gasket
Float Valve
Pilot Screw
Pilot Screw Spring
Pilot Screw Flat Washer
Pilot Screw Oring
Needle
Needle Jet
Needle Jet Clip
Main Jet #130
Slow Jet #38
Primary Jet #45
Bowl Rim Oring
Drain Screw Oring

1986/87 Kit Inventory

Bowl Gasket
Top Plate Gasket
Float Valve
Pilot Screw
Pilot Screw Spring
Pilot Screw Flat Washer
Pilot Screw Oring
Needle
Needle Jet
Needle Jet Clip
Main Jet #130
Slow Jet #38
Startup Jet #70
Primary Jet #45
Drain Screw Oring
Idle Knob Spring
Idle Knob Bolt
Idle Knob Washer

As you can see, the two kits differ by six parts. The absence of the bowl rim oring does not effect the carb operation. If you look at the bottom of the linkage cavity you will see a drain hole. That hole continues through the bowl. The oring provides a seal between the linkage cavity and the outlet on the bottom of the bowl. Its job is to provide a leak path to drain the linkage cavity if it gets filled with water.

The other differences are pretty obvious. Honda redesigned the jet stack in 86, they integrated a screw in type startup jet with a larger hole fixing the cold start issue the 85 carb has. The 85 startup jet was pressed in. There used to be a kit to fix this problem but if the jet is removed, drilled to .80mm and reinstalled then the cold start issues go away.

So this is where I start now that the kit differences have been outlined. An 86 kit will work in an 85 carb but you will be short the primary jet and bowl rim oring but you will get the idle knob hardware.

On the rim of the body just under the fuel inlet nipple, there is a number identifying the carb. Here is the breakdown of the numbers and their application.

QA01A - 85ES
QA02A - 85SX
QA04A - 85 TRX250 (this carb will not allow the ES or SX to run right)
QA05A - 85 350X
QA07A - 86/87ES
QA08A - 86/87SX
QA09A - 86/87 TRX250
QA10A - 86 350X (nobody makes a kit for the 86 carb and the slow jet is larger for 86 #45. If you put an 85 slow jet #42 in an 86 carb, the motor will run very very lean at idle to the point where the head pipe will glow. Be aware of this)

I will continue this tutorial tomorrow. Please no posting yet. thanks.

[Flyingw]

To elaborate on the 85 ES/SX cold start problem I mentioned. This mod only applies to the 85 ES/SX carbs and is really only a problem for you in really cold environments. In a nutshell, because the startup jet metering hole is so small, it doesn't provide enough fuel to fire a cold soaked motor but I'm talking 30deg F or colder. None the less, it couldn't hurt to do this mod no matter where you live. I have attached the original Honda Service bulletin along with pics of how I pry the jet out. You want the modified screwdriver to be about horizontal. Gently push down and the jet should come out. I use a .80mm micro-drill and a Dremmel to drill it out. I have encountered many ES/SX carbs where the startup jet was plugged with debris. You will need a #4 sheet metal screw, a modified flat blade screwdriver and anything with about a 1/4 - 3/8 diameter to lay on the jet stack to act as a pivot. Screw the sheet metal screw in about 1 - 1 1/2 turns. Don't worry about damaging the jet with the screw. The metering hole is farther down than the screw will reach. Pry the jet out, drill it, and reinstall. While the jet is out, be sure to shoot carb cleaner through the hole. If doing a carb rebuild, leave the jet out until final assembly. A set of metric micro-drills can be found at most local tool stores or on the internet for just a couple of bucks.

I have a set similar to these. You will need a Dremmel with a chuck to use these.

http://www.ebay.com/itm/New-15pc-Micro-Drill-Bit-Mini-Set-High-Speed-Metric-Sizes-0-3-mm-1-0-mm-/190828244487?pt=LH_DefaultDomain_0&hash=item2c6e3fee07

[Flyingw]

Lets continue with the initial disassembly. For this I'm using a TRX250 carb but the ES/SX/X carbs are the same.

The very first item I always remove is the pilot screw. The reason is if the pilot screw is seized, it will more than likely snap the head off and that may dictate whether the carb is tossed. If the head does snap off you have a couple of options.

1. Drill the screw and try to extract the pilot screw with an easy out
2. Cut a slot in the pilot screw and try to use a flat blade screwdriver to turn the pilot screw out
3. Use a large drill and drill out as much of the pilot screw as you can. If you use this method you run the risk of damaging the thread in the carb body

With any of the three methods, applying some heat is always good but keep in mind the carb body is cast aluminum so you don't want to make the metal glow, just heat it. I could do an entire thread on the pilot screw extraction methods so for the purpose of this thread, I will assume the pilot screw came out ok.

Tools needed
#1 Flat Blade Screwdriver
Pick with a fine tip bent with a hook or something similar (This is to get the flat washer and oring out of the hole)

Remove the pilot screw, spring, flat washer, and oring. Be sure these parts come out. I have seen carbs with no flat washer and oring so take a flashlight and shine it in the hole ensuring all the parts came out.

None of these parts will be reused but set them aside until the rebuild is complete.

All parts are accounted for.

[Flyingw]

Remove the vent hoses and bowl drain hose. Turn the carb on its side and remove the cover if not off already and idle adjustment knob. Set all the parts to the side.

[Flyingw]

On the 350X carb, remove everything listed above as well as the choke lever, choke valve, idle knob, and its associated bracket.

Tools needed

#2 Phillips
14mm Wrench

[Flyingw]

If you have the need to chase the pilot screw hole threads or the choke valve hole threads, Wonderboy has determined the tap needed is a plug tap 6mm x 0.5 and they are available online.

http://www.amazon.com/6mm-High-Speed-Steel-Plug/dp/B0006FI7TU

The choke valve hole threads are 12mm x 1.0

http://www.amazon.com/Metric-Right-Thread-1-0mm-Pitch/dp/B007HHTBYA

[Flyingw]

The next part to disassemble is the top of the carb.

Tools needed

#1 Phillips Screwdriver
#2 Phillips Screwdriver

Remove the three screws retaining the top cap. Remove the cap and old oring and set aside. Next remove the #2 Phillips screw and lock washer retaining the actuation arm to the shaft. Now it's time to remove the two #1 Phillips 3x6mm pan screws holding the linkage to the slide. These screws like to corrode to the slide. You basically have one shot at getting them out without boogering the heads. To do this, I set the carb on a firm surface. I take the #1 Phillips screwdriver and set it on the head of the screw. Now push down firmly as you apply torque to loosen the screw. Steady even pressure and the screw should break loose. If you booger the head then the only recourse is to drill the head. Not a good option so be careful. Also keep in mind the slide has a Teflon coating to allow the slide to move freely without any lube. Protect the slide. Once you get the two pan screws out, remove the slide and linkage and set all the parts aside.

[Flyingw]

Let's separate and disassemble the bowl.

Tools Needed

#3 Phillips Screwdriver
#2 Flat Blade Screwdriver

Remove the drain screw
Remove the oring on the drain screw
Remove the four #3 Phillips screws retaining the bowl
Separate the bowl from the carb body
Remove the old bowl gasket
Remove the old oring on the rim of the bowl

Set all parts aside

[Flyingw]

On the 350X carb, remove the jet access plug on the bottom of the bowl with a 17mm wrench.

Remove the oring from the plug and set aside

[Flyingw]

Ok now we're to the meat of this rebuild but I would rather have an ES/SX carb to illustrate from. I have an ES carb coming in from Colorado but it won't be here for a few days so I am going to pause right here until it comes in. I'd rather not pull my carb and disassemble it but if any one of you has an ES or SX carb that is complete and are willing to take several pics I can use for illustrations then I have no choice but to pause here. If you do and are willing, shoot me an email to jamesbaldwin99@gmail.com and I'll let you know what pics I need for completing the disassembly. I have a couple of pics of an 86 carb to illustrate the jet stack with but not the right pics for the 85.

[Flyingw]

Thanks to Wonderboy A.K.A Frank and his camera I can finish the disassembly. In my last procedure I removed the bowl, now let's get the float and jets out. As you can see in the first pic, the bottom of the carb with the jet holder (Baffle), float, and the jet stack. The second pic shows the jet holder removed and the third shows the float, float pin, and float valve removed.

[Flyingw]

Now lets remove the jets. I didn't ask Frank to remove the jet from his carb but I will illustrate each jet and their position. Removing them is pretty self explanatory.

Remove the main jet
Remove the slow jet
remove the primary jet

If your doing the cold start mod, remove the startup jet per the instructions in post #3.

Set all parts removed aside

Note: on the TRX250 carb (QA04A) and 85 350X (QA05A0, the primary jet is omitted) In fact the hole is not through drilled or tapped.

[Flyingw]

Remember I said in 86 Honda redesigned the startup jet. If you look at the side of the jet stack you will see a hole up toward the top of the jet stack just above the startup jet. In 86, Honda put a screw in jet. If you're working on an 86 carb, remove the rubber block off plug and screw in startup jet. The same goes for the 350X carb. If your 86 carb does not have a rubber block off plug, don't worry, the hole its blocking is not through drilled. To tell you the truth, I'm not sure why Honda put a rubber plug in that hole.

[Flyingw]

Think I'm done with disassembly? Not so fast. There are still three parts to remove.

Needle Jet Holder
Needle Jet
Main Nozzle

Unscrew and remove the needle jet holder with a 7mm wrench and set aside

Using a small punch or small drift, come down through the slide hole and push out the needle jet. It will fall out of the needle jet holder hole.

With the primary jet removed, reach in with your finger and push the main nozzle down. It should fall out of the primary jet hole. I don't have an extra main nozzle to illustrate but when I get my carb, I will insert a pic of it.

So that pretty much completes disassembly. I don't remove the butterfly, butterfly shaft, or spring. They are a total drag to reinstall more specifically getting the spring set and wound correctly so I leave them in.

I am going to wait until my carb gets here before I get in to the next set of procedures as I will be actually doing a rebuild on it so this is a good time to field any questions you may have concerning the disassembly.


END OF DISASSEMBLY POSTS #1-15

[Flyingw]

Alright guys, pressing on. I purchased four carbs off Ebay. All four were sold as parts carbs and I guess I was expecting more but once I received them I understood why they were being sold as parts carbs. The first one came from Colorado. It had some corrosion issues but mainly the choke valve was fused in the hole. I soaked it with some Silicone lube for a while and it came right out. When I went to the disassembly I realized the butterfly shaft didn't want to move. I told you that I typically don't take the butterfly shaft or the slide actuator arm out but in this case I had no choice if I wanted to save this carb. When removing these assemblies, the butterfly is the first thing to remove but even it was fused in the shaft and I destroyed it getting it out. I was able to get these assemblies out and clean up the two shafts to where they rotated as they are supposed to BUT now I didn't have a butterfly to put back in from an ES but I did have a butterfly from an SX. I went ahead and rebuilt the carb with the SX configuration and thought I would use one of the others for the reassembly demonstration.... HA!!!!!!!! I'll get to those in the next post. Here is the Colorado carb before and after. I'm hoping it will run just fine but we'll see tomorrow.

In the pictures you will see the difference between the ES and SX butterfly. This is the one and only difference between the ES and SX carbs. The hole and the metal treatment. I really don't know what that hole does. Do you? They are both made of aluminum and are exactly the same shape and dimension.

I also inserted a pic of the main nozzle in post #15. One thing I will say about the main nozzle. If your trike won't run right unless the choke is on, this is more than likely the culprip. A clogged up main nozzle. I run this through the bead blaster along with the needle jet holder. Over time these two parts will build a layer of film from fuel. The holes drilled in these two parts will actually grow smaller albeit not by much but it's enough to effect the way the carb works. Bead blasting ensures all the film is removed restoring these two parts back to their original condition. I'm convinced this is a large part of the problem with these carbs. When rebuilding these carbs, be sure these parts are as clean as you can possibly get them. The needle jet comes in the rebuild kit. Be sure you replace that every time as they are matched to the new needle. This is very important!!!!!!

[Flyingw]

Moving on. After the carb has been disassembled, I soak it in Heptane. I get this as a waste product from work but not everybody has Heptane sitting around so, go to the drug store and but some big bottles of rubbing alcohol and soak the carb in that. Get a container big enough to pour enough rubbing alcohol to completely submerge the carb. I also soak the bowl and all the other parts I'm going to reuse. The key is clean clean clean. Even if you aren't going to bead blast your carb, do this anyway. Get your carb as clean as you can. For me, this step is to ensure there is no oily residue present to attract and hold glass bead. Soak the carb overnight and blow it out thoroughly with compressed air. Carb cleaner can also be used. Be sure to stick the straw in every single hole in the carb and shoot that stuff through. Every hole should blow through to somewhere else. If a hole doesn't blow through, you have an obstruction and it will need to be worked until it does blow through.

[Flyingw]

Wonderboy asked me if I would outline what I do to prep the carb for bead blasting so here are illustrations of what I do. I stuff the venturi and slide hole with blue paper towel. I also stuff the float valve hole, choke valve hole, and pilot screw hole with wads of paper towel. This is to protect the seats from being hit directly with the glass bead. No matter how hard you try, glass bead is going to find its way in to the carb so don't worry too much about it.

Now, I'm going to say in big bold letters here.... DO NOT BLAST YOUR CARB IN THIS MANNER WITH SAND!!!! DO NOT USE SAND. The properties of sand are completely different than glass bead. Sand has irregular edges, is very aggressive, and hard to control. Glass bead on the other hand is round balls of glass, the size is very consistent, and easy to control. DO NOT USE HARBOR FREIGHT GLASS BEAD!!! that stuff is junk. Its full of debris, and it has LEAD in it. Find a local dealer that sells US made glass bead. I found a #12 glass bead work great in these small syphon type cabinets. I have an inexpensive benchtop blast cabinet. I removed the cheap ass florescent light that came in it and installed 4 120v under cabinet puck lights. I put a regulator on it with a water separator and have a small vacuum plumbed in to it. I bought an assortment of inexpensive wire baskets from Office Max to put parts in to. This setup works very well. I have the pressure set at 60psi. Anything over that is just destroying the glass bead faster with no added benefit. I dump about 80lbs of glass in it as you can see. I run my rubber parts through it. It takes 25 years+ of dirt and grime off and makes the rubber parts look almost new. Far better than a toothbrush and Dawn dish soap.

[Flyingw]

Going back to the parts carbs I bought. I bought four carbs but one of them was a TRX250 carb leaving two 85 ES carbs. One I rebuilt last night came from Colorado and the others came from Canada. One of them had a broken screw on the top cap, butterfly shaft was frozen, and the choke valve was totally fused in the hole. The other had corrosion, the slide wouldn't move, and the idle adjustment bolt wouldn't turn. Both of them I had to take out the butterfly shafts and slide actuator shafts. I got broken idle bolt out with a little heat but that damn choke valve was another story. I soaked it, heated it and finally drilled it. It took me about two solid hours on just the choke valve alone. The simple broken screw on the top cap on the first one turned out to be a major fiasco. I drilled it and stuck my easy out in it. Hit it with some heat and of course the easy out snapped off. In the end I managed to drill a hole through but it was slightly off center. If that carb works, I'll leave it in my SX and sell the one that came out of my SX. If it don't work, it will get stripped for parts. I already have a guy on the hook for the Colorado carb providing it works so we'll see how the other two work once I get them reassembled. More to come on those. That's it for tonight. I'll get the butterfly and slide actuators put back in both tonight and pick back up tomorrow night with the assembly on the two Canada ES carbs.

[dougspcs]

Masterfully done Jim, here I was thinking "he's crazy showing how it's done..he's handing away the keys to FlyingW bus"

But as I see the process and level of attention to detail I see you haven't anything to fear..you'll still get just as much work.

Many like me will look at that and say 'screw it, I'll send it to Jim!!'

Of the 10 people who attempt to draw from your instruction, 8 will botch their carbs because they lack the skilled hands and experience you have!

I realize you're not giving people the 411 to take money from your pocket..you're showing everyone the incredible detail put into a FlyingW carb. Smart business!!

Or did I read it wrong and you really trying to reduce your workload by showing everyone how to DIY? If so I think it backfired!!

[Flyingw]

Thanks Doug, I appreciate your words very much. I started this not to make money by any means. If I did, these carbs would be 400.00 carbs. At that price I'd have a bunch of rebuilt carbs sitting on my shelf. Money is tight for everyone these days even with me but there is also value for me having something to do. I started rebuilding these carbs because so many guys were having problems with their carbs and I had several sitting in my attic not doing anybody any good so I pulled them and got them rebuilt and its blossomed from there and truthfully, I did it in large part because I was bored. I'm not one to just sit around with nothing to do. I have to be engaged with something or I get cabin fever real easy especially in the Winter months. I know most guys are like me and would rather do the work their selves. This is why I do my own powder coating. I have a DIY Zinc plating kit I use on onzie twozie items, and one of these days I'll do a tutorial on rebuilding the ES/SX differentials although the lack of available special tools has kept me from doing this. I have the tools but average Joe trike owner doesn't so I'm on the fence about that tutorial. This tutorial pretty much applies to any of these 3wheeler carbs. The part arrangements vary but the basics are all the same. I am more than happy to do these for our guys and if the day comes that nobody needs my services then I'll move on to something else to occupy my time. Either way, I like to be useful and engaged. I'll press on with the assembly later tonight.

[bumsted200s]

I've read thru your entire post, all I can say is well done. Funny I logged on during lunch (at work too) to just see whats all involved re-doing a '85 250SX carb the correct way. My saturday is going to involve taking apart a 250SX carb for a friend. Have the 185/200X stuff down pat but these not so much. But this is going to work out perfect have a step by step to follow. And re-assemble posts to follow. Thanks for sharing


Brian

my wheelers:
1981 Honda 200 5 wheeler
1982 Honda 200 Hondapotomus
1982 Honda 185S
1982 Honda 250R
1984 Honda 200S
1985 Honda 200S
1985 Honda 200X

[Flyingw]

I'm glad people are finding this information useful. I'll get back to the assembly hopefully tonight.

[Flyingw]

Assembly!!!!!! Before I get in to the assembly, there is one product I'm going to strongly advise all of you DIY trike mechanics to add to your chemical inventory. Its trade name is Petrolatum. Petrolatum is a brownish paste and is sold as a corrosion preventative grease but it also conditions and lubricates rubber parts. Not only do I use this stuff in the carb assembly but I use it for many other assemblies like assembling the brake calipers, brake master cylinders, differential assembly, engine assembly, and I even lube my rim beads when I mount tires. Petrolatum conditions rubber and stays in the rubber although it is dissolved by fuel and solvents but not by other oils and greases. Anything rubber like orings and orings will get noting but benefit from Petrolatum. Remember I said I run my rubber parts through my bead blaster? After the rubber parts come out of the bead blaster, I take a toothbrush with Petrolatum on it and scrub the Petrolatum in to the parts. I then take a rag and rub it in to the part and rub the excess off making the part look like new. Anybody in the aviation mechanics industry knows what Petrolatum is and what it does but most guys don't. I am here to tell you, it is GOLD when working on these old trikes. Its a little spendy but there is nothing that is useful than Petrolatum. Its made by several manufactures but What I have is made by Castrol Industrial under the name Braycote 236 (VV-P-236A). As I said, I use this stuff on so many things like household plumbing and working on my vehicles. Anything rubber!!!!!! Petrolatum is also the base product in some antibiotic ointments like Neosproin.

Braycote 236 MSDS
http://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/42C64CA08BC03FD780257796002F8753/$File/457048_XI_en.pdf
http://site.skygeek.com/MSDS/braycote-vvp236-1lb-236-petrolatum-1-lb.pdf

Source of Supply
http://www.skygeek.com/braycote-236-petrolatum.html

http://www.ebay.com/itm/Castrol-Braycote-236-Braycote236PT-One-Pint-VVP-236A-Petrolatum-PT-/170803431827?pt=Motors_Aviation_Parts_Gear&hash=item27c4ad8993&vxp=mtr

http://www.mil-specproducts.com/Product-Equivalents/PETROLATUM,-TECHNICAL

[Flyingw]

The first part I always start with is the bowl. I lay Petrolatum in to the groove for the bowl seal. This is mainly to hold the seal in place when I set the bowl on the body to form a good seal. When the carb gets its first fuel, the residue Petrolatum will be dissolved and the bowl seal will swell making a good tight seal so not to worry. I then place the oring on the drain screw and wipe some Petrolatum on the oring and screw threads and install the drain screw. The last thing to install on the bowl is the oring on the rim of the bowl and it too gets lubricated with Petrolatum. Remember, this seal is not included in the 86 kits so you will have to reuse your old seal. Set the bowl aside.

In the absence of Petrolatum, Vaseline can be used or even Neosporin ointment. Remember the purpose here is to hold the bowl seal in place and to lubricate the two orings.

I want to also mention again here that if in the future you have to take the bowl off the carb, the bowl seal will be larger than the groove. It's supposed to do this. Wash the seal off with rubbing alcohol and hang the seal in an oven at about 150 - 200deg for about 10 minutes. Let it cool. It will shrink back to its original size. Trust me, it does.

[Flyingw]

The next step is to assemble the bottom of the carb. Main nozzle, primary jet, startup jet, slow jet, needle jet, main jet holder, main jet, float valve, float, float pin, and baffle. I start with the needle jet.

If you look at the needle jet, you will see a flat end and a cupped end. THE CUPPED END ALWAYS GOES FIRST. Drop the needle jet in the hole cupped end first.

Drop the main jet holder in the hole. You may have to wiggle it around to get the needle jet to start in to the hole but when the main jet holder threads, its aligned so screw in the main jet holder and tighten it up. A little more than snug is all that's required.

Drop the slow jet in the hole and tighten it up. (Be sure it is screwed in all the way)

Install the startup jet. Tap it with a small hammer or something similar. (on 86 carbs, screw the jet in to the side of the jet stack)

Drop the main nozzle in the hole small end in first then install the primary jet and tighten it up

Set the float valve on the float and install the float and float pin.

Install the baffle

Set the bowl on the carb and install the four 4x14 screws. Don't forget to set the vent tube holder under the back left screw. Tighten the screws a little at a time using a cross pattern. Don't over tighten these screws. The illustrations will be spread between this post and the next post.

[Flyingw]

Second set

[Flyingw]

The last part of the bottom of the bowl is the pilot screw. Be sure you have the assembly order right. Screw, spring, flat washer, oring. Assemble the pilot screw and put a little lube on the oring. Install the oring screwing it all the way in until it stops then back it out 2 turns for 85 and 1 1/4 turns for 86/87 carbs.

NOTE: The pilot screw does not get an oring on the head.

[Flyingw]

The next assembly is the slide needle, slide, actuator arm, and top cap.

Per factory settings, set the C clip on the needle in the second groove and drop the needle in to the slide.

Drop the slide in to the carb hole. Ensure the slide moves freely up and down. No binding. No lube of any kind goes on the slide. The slide has a Teflon coating.

Set the arm set on the on the actuator arm pin and lower the arm set down inside of the slide aligning the holes. The flat side of the arm set aligns with the middle of the slide.

Using a #1 Phillips, install the two 3x6 pan screws locking the arm set to the slide. (Trick... I put a dab of Petrolatum on the end of the Phillips to hold the 3x6 screw to the end of the screwdriver otherwise you'll go out of your mind trying to install those small screws without dropping them off of the Phillips)

Install the 4x13 pan head screw with the lock washer in to the actuator arm locking the actuator arm to the arm set.

Like the bowl gasket groove, I fill the top cap seal groove with petrolatum, install the seal and top cap and secure with the 3 4x8 pan head screws

[Flyingw]

Last few pics of the carb top.

[Flyingw]

Now for the linkage side of the carb. Do not install the idle screw yet!!!! The next step is very important but before we make the synchronization adjustment, I want you to rotate the linkage as the cable would ensuring the butterfly and slide linkages rotate freely and return all the way back. I shoot a little silicone lube through the two springs and work it in to the two shafts just as an added measure. If all rotates as it should lets do the synchronization adjustment.

This adjustment is critical to ensure the slide and butterfly move together at the same time. Over time, the tab on the slide linkage will bend up. this is exactly why this adjustment exists. The split plate on the linkage is how you make this adjustment but I will typically bend that slide arm tab down a little so the split plate isn't spread so far.

With a pair of needle nose, bent the tab back down if it bent up too far. With the slide all the way down, spread or pinch the split plate until the split plate just barely touches the slide arm tab. I actually use a loupe to help me see when the two touch. Now rotate the linkage a few times ensuring the linkages rotate and return back all the way and the tab and split plate are still just barely touching. Once this is done, assemble and install the idle adjustment screw but do add some lube to the end of the screw before you install it. Thread the adjustment screw in until it contacts the throttle cable linkage. From this point I usually give it about 2-3 turns so when I do my initial engine start, it will start and fast idle then you can adjust the idle to your desire. I set my idle to 1200-1400 rpms.

Again, I cannot express to you how important this adjustment is to the proper operation of the carb. If the slide and butterfly are not in synch, the motor will do all sorts of funny things like fall on it face when you hit the throttle. Pages 4-12 and 4-13 give you the factory steps to this adjustment and pages 4-14 and 4-15 in the ES manual.

[Flyingw]

Alright, we're rounding 3rd and heading for home....

The last thing to do is install the bowl drain tube and the two vent hoses. The 86 model carbs had this spaghetti mess of vent tubes. I rebuild my carbs with two simple vent tubes. I buy 5/32 vacuum tube from Autozone. For fresh tubes, you will need about 18" of vacuum line. For the bowl drain tube, I cut a length about 10" long and the two vent tubes are about 4" long but you can cut these any length you want. Install the bowl drain tubes and vent tubes.

Well that's it fellas. For me, the next step is to install the carbs on my SX and test them. The last adjustment you may or may not need to do is adjust the pilot screw. The symptom if you DO need to adjust the pilot screw is the motor will fall on its face it you hit the throttle. With a warm motor, choke off from idle hit the throttle. if the motor falls on it face turn the pilot screw IN 1/4 turn at a time. This fattens up the pilot circuit but of all these carbs I've sold, only one guy reported to me that he had to adjust the pilot screw. From sea level to about 2000 feet, it should be good to go.

You guys are free to post away. let me know if you have any questions or is confused about anything. This is the process I've been following and it seems to be working as I've sold about 20 of the ES and SX carbs. Good luck with your rebuild and as I said before, these procedures pretty much apply to any of these 3wheeler carbs you have.

END OF TUTORIAL!!!!!

[atc007]

Well Jim. I have been doing these carbs more decades than I care to remember. All with great results. But you my friend have taken it clean over the top! It is SO cool to see you mix in what you've acquired in the aircraft industry to this! I never heard of that goop. But I will have a tub soon :). I have found over the years that I prefer solely. NAPA carb soak for carbs. You MUST remove any and all parts that will be eaten! Rubber,o rings etc. And as you said. Restoring any and ALL little holes in any carb is crucial! Rather glassing them or drill bits ,whatever. It is essential.This tutorial, now available to any and all who want a as new OE Honda carb, serves as a school to even some seasoned techs working in shops! I can't thank you enough for the time this must have taken you. I can only imagine. Consider the deal we were talking about done as a small token of thanx. Email me your ppal if it's all still available. This is 1st class all the way :) Thanx Jim .

[MRSOUND]

Thanks for the step by step Flyingw! Having a sx & es I WILL be using this tutoral over the winter to rebuild both. Subscribed to the thread first day so I could following along and now have it book marked for later reference! Awesome detail with pics....don't get any better. Thanks again.

[Flyingw]

Thanks guys. That means allot coming form you. What good knowing all of this if others can't benefit from it. As I said, I don't do this to pay bills, I do it for fun. If I had to do this to pay bills, it wouldn't be any fun at all.

Bill, I sent the SX diff home with Filthyhat yesterday simply as a time saver for him but I do have his diff and its in beautiful shape. I just need to give it a fresh coat of paint and rebuild kit and it will be good to go. I want Filthyhat to get his rear end installed and tested before I do anything else. After that then yes, we will do something up.

[Flyingw]

One note to the rebuild of these QA series carbs. Bill mentioned above those carb soak chemicals. That chemical is very nasty stuff. It works very well but is pretty aggressive. On the three parts carbs I bought, I had to remove the slide actuator and butterfly shafts from the carbs. What I learned on these is there are two felt seals in the body of the carbs. Their job is to provide a debris seal for crap working its way down the shaft hole. I'm pretty sure the carb dip will dissolve the felt. I had no idea they were in there until I started seeing bits of felt in my blast cabinet. The air pressure had knocked the seals out. Luckily I only lost two seals so I cannibalized both seals from this carb and replaced them.

As for the assembly of the 350X carbs, the variation of the assembly process should have included the different idle adjustment screw assembly and the choke valve and lever assembly but those are pretty self explanatory. One other thing to note, the 350X carb is considered an upgrade to the ES/SX motors. They do fit just the same as the ES/SX carbs however, you can omit the X choke valve and lever and install the stock ES/SX choke valve and use it the same way it was designed for and that is with the choke cable. It screws in all the same. If fact I have a 350X carb to test along with three other ES carbs. The X carbs runs very well on the ES/SX motors with a little tweaking to the jetting.

[atc007]

Yes indeed. The soak will eat the felt. It will also ruin/eat,all plastic bushings. I soak only where it's safe/or completely disassemble the throttles :(( Like you said. they all need synced when they're done anyhow. I have seen one TRX 250X and one TRX 300EX actually break the idle adjustment arm clean off before! These are very serious springs. I won't get into how nice and soft you can make your throttle push by playing with the spring. Better to live with them stiff :)

[Flyingw]

After fussing with these three carbs, I have figured out how the two connected shafts have to go back in. The butterfly plate can be a big pain to get back in even though its symmetrically cut out, the way its worn dictates which way its tuned and flipped to set it back in the right way and is easily damaged using the wrong tool to grab it with. But now I know. I thought about adding that to this but trying to convey how I have to flicker the shaft to set the butterfly in to its groove might be a little difficult but I figure most guys won't mess with that anyway.

[Flyingw]

Oh, and since the shafts were vacated from the bodies, I didn't bother masking anything off for bead blasting. I just made sure to not hold the gun nozzle over any of the sensitive holes. All the holes blew through. The only thing I couldn't get out was the nozzle tube under the startup jet. Its a very mild interference fit and couldn't figure what I could stick in there and grab the tube to pull it out without damaging it.

[Big G]

This is great Flyingw! Awesome to see you took the time to put this thread together. I'm sure it was no easy task - especially with all the photos and diagrams you included. I'll be referring to it in the future because unfortunately I have the dreaded cold start issue with my '85 250ES. Actually, on second thought, I think I'll just send it to you and have it done right :)

[Flyingw]

Copy that Big G. I can take care of it.

[Flyingw]

Tonight I tested five carbs, four 85 ES carbs and one 85 350X carb. All but one checked out. The one that didn't run to my satisfaction is the carb I got from Colorado. If you recall, that's the one I put the SX butterfly plate in to. The carb appears to be running lean. The motor has a slight pop on deceleration and at idle the motor seems to be running hot. I'm going to pull the carb apart and go back through it but I'm find myself wondering if the butterfly plate has anything to do with it. If I had an ES butterfly plate I'd be inclined to drop it in there and see if it runs the same but I am out of those.

[Dirtcrasher]

Great work as always Jim!!

Glad to have you in the "trike" industry..... :D

[dougspcs]

One thing for sure, I'm keeping this thread link handy..

We will be referring back to it for years to come..every time a newb asks why their machine is running like crap!!

A great piece of reference material that is unarguably the bench mark to aspire to..if yours doesn't even come close to looking like this..go back and do it again!! Until then, no more questions!!

Carb threads are getting for me what oil threads are to Fabio!

[atc007]

To be fair though. On a Mikuni/Yamaha/Suzuki. All you need are .A. Parts that are still serviceable. And B. Pilot and main circuits that are still open. That's it lol. These Keihins are arguably the most complicated 3 wheeler carbs there were. A newb asking a carb question would be WAAAYYYYY Overwhelmed looking at this thread when all he needs to do is blow out the pilot and main air and fuel circuits and ride lol...

[MRSOUND]

I think this thread has the makings of being a STICKY! I think one of the mods should make it happen.

[Mosh]

Great write up. I have been through my share of carbs and the tips you show took a lot of time for you. I learned something new in this tutorial.

Now.....I would LOVE to see a rear diff write-up. I know I will need to re work the ring and pinion in mine eventually. I have presses and pullers and race removers and drivers. More importantly is where to get new gears? Mine are pitted from moisture.

[dougspcs]

To be fair though. On a Mikuni/Yamaha/Suzuki. All you need are .A. Parts that are still serviceable. And B. Pilot and main circuits that are still open. That's it lol. These Keihins are arguably the most complicated 3 wheeler carbs there were. A newb asking a carb question would be WAAAYYYYY Overwhelmed looking at this thread when all he needs to do is blow out the pilot and main air and fuel circuits and ride lol...

Ok point taken..the learning curve is kinda steep!!

But if it comes down to does your carb look like this..??

178818

Or like this??

178819

If the answer is #2, then you should at least attempt to read Jim's awesome thread..

My point is too many new members run to the computer to ask before even attempting to look at the machine..this thread is all the reference material you need and more.

Sure it's a long read, but totally worth the effort..if it's too much then box it up and send it too Jim and he'll send it back looking like #1!!!

[dougspcs]

I think this thread has the makings of being a STICKY! I think one of the mods should make it happen.

Mr Sound is right..but I'll take it one further.

If Billy made an 'experts' page..this would make a great entry. Then the rear differential build thread..? I know there are others. Perfect reference material for members old and new!!

[Flyingw]

All good stuff guys. I do have a few differentials to rebuild and since I have nothing but time on my hands right now, I will do a diff rebuild thread. I have a perfect candidate sitting on my bench for that. Be looking for that in coming days.

Now, does anybody have a trashed 85 ES carb you want to part with. I need the butterfly plate out of it. This Colorado carb is really pissing me off. I pulled it apart again last night and I could not find anything that would cause it to run lean. I have it installed in my SX right now with the airbox all hooked up. I'm going to take it for a ride around the hood and see how it runs under load but I'm thinking the butterfly plate has something to do with it which still doesn't make any sense to me. As I pointed out, the SX carbs have the hole in the butterfly plate as well as the TRX250. That's where I got the butterfly plate from but I'm still wondering what the hell that hole is there for. Why one set of carbs and not the others? One of those things that makes me go.....HMMMMMMMMMM.

[atc007]

That hole has to be primarily effective at idle only. Sure it could disrupt airflow a very slight amount when in the thumb,but I wouldn't think anything at all noticeable except at idle. I have noticed the holes before,but never had a problem either way. My bet is the right plate will fix er right up.Wish I had one,I'd send it your way. Well, ok , I have lots of carbs lol. None apart. But I will send you a sx and a es if this one doesn't cooperate with you.

[Flyingw]

Doug has some junker carbs he's going to send me. Hopefully one has a good plate in it. I tend to agree Bill. The only time that hole would have any effect on the carb is when the butterfly is closed. Its adding a small amount of metered air at idle only but why? I'm half tempted to put a piece of speed tape over the hole and see if it effects it. I think I'll do just that.

[Flyingw]

Well I took my SX out and on the gas it actually runs pretty good but it does have some popping on deceleration and idle is very erratic. I think I'm going to pull the carb and rip it apart again and concentrate on the slow speed circuit but I will go back through it thoroughly and I will block off that hole in the butterfly plate and see what I get. If that doesn't fix it then more than likely I will strip it for parts.

[Flyingw]

Tonight I went back through the Colorado carb. Everything looked good. I blocked off the hole in the butterfly plate with a drop of 2 part epoxy and guess what? An entirely different running carb???????? It idles smoothly and the popping is gone. WTF!!!!!! Now I really want to know what the hell that holes does.

[atc007]

It adds air at idle and deceleration resulting in lean. End of thinking lol. But seriously,was this 85 only SX's or 86-7 also?? I'll have to pay more attention looking through parts and take notice. The things manufactures change year to year never ceases to blow my mind.

[roonie]

absolutely terrific post. Can you tell me.....where physically on the carb, does the fuel leave the carb to enter the engine. where does the fuel travel from? Also how is the fuel pumped....by vacuum from the piston? Or is there an actual pump located? I have an 85es that im about to delve into. thanks

[atc007]

Fuel is screened through a tube in your tank,then into the petcock where it goes through a screen. All gravity ,no pump. Down the hose into the carb ,down to the needle,if the floats are calling for fuel,the float is down opening the needle and seat allowing fuel in. Once the floats are happy,they push the needle up into the seat shutting fuel off.With fuel in the carb bowl,the relative circuits mix the fuel and air together" spraying "the mist into the intake. The down suction of the piston draws it in. These particular carbs are simply,over complicated. With a butterfly AND a vacuum, Rather than just a slide. FCR carbs are what you want these days. But that is a whole other story. There ARE machines using a fuel pump. They are the bikes with the tank under the seat where gravity won't do the trick. A vacuum pulse from the intake runs the pump on these bikes.

[Flyingw]

Bill,

The SX carbs 02 and 08s and the TRX250 04 carbs are the only ones with the hole in the butterfly. I'm going to compare the various holes in the carbs and see if some are larger than others.

Roonie, these carbs are all vacuum type carbs. There are 3 ports corresponding to the three circuits in the carb. There is a tiny hole just outside and forward of the butterfly in which fuel is fed to the motor for the idle circuit. The main nozzle sticks up just behind the butterfly feeding fuel to the motor for the slow speed circuit about 1/8 to 40% throttle roughly and the main jet feeds the motor fuel at about 40% to wide open and that fuel comes from the hole the needle passes through. All vacuum drawn. All fuel is drawn from the bowl. Does this help?

[roonie]

"Does this help"...yes incredibly so. So it must be imperative that the air box/filter/ etc. be installed before start up eh? Other wise there would be tons more air entering the system..no? Im Canadian..eh. Thanks all you guys for answering some real corny questions. Now im off to install the new carb kit that did NOT come with a float. The kit is a "Shindy" brand made in japan....any good? thanks

[Flyingw]

Yep, Shindy is just fine.

[roonie]

flyingw .....on the second page....you state..."drop in the main nozzle in the small end in first then install the primary jet and tighten up".....is this for the 86 model only because i dont have one of those and im quite sure when i dismantled this carb that there was not a primary jet. I dont think i recall seeing a second brass part poking through the carb throat.
I never got a new one with my shindy kit either but i see either did your 86 kit in your pics. I do however have the slotted/threaded small part that screws into that same hole atop the primary. So....should i have a primary jet. Could this machine run without one all these years or should i get on my hands and knees on the shop floor now?

Its interesting that there is two labels on the shindy bag..one underneath states 1985 250 es and the sticker placed overtop that one says 85-87 250es

[Flyingw]

STOP RIGHT THERE!!!!! What is the QA number on the bowl rim under the hose nipple? QA04A, QA05A, or QA10A. Answer that first.

[Flyingw]

Also, is there a large spring in your Shindy kit? Its the spring for the idle adj screw.

[roonie]

STOP RIGHT THERE!!!!! What is the QA number on the bowl rim under the hose nipple? QA04A, QA05A, or QA10A. Answer that first.

HI..the # is QA...then underneith its 01AAWJt....its a funny looking t. Also....the second A in that sequence has a square around the letter A. As far as the spring for the idle adjustment, yes i got one of those and a new screw and washer too but no black knob. I am in Canada so im guessing its a canadian bike....eh

[Flyingw]

So, yours is an 01A. Look a the pics and your kit. The carb you have is an 85ES and the kit is for an 86ES. Compare the pics I laid out of the two kits. The main nozzle does not come in any kit. That part is essential. The Primary jet used to not come with the 86 kit but I got an 86 kit the other day that had one in it. Fluke, maybe but historically the primary jet is not in the 86 kits. If the jet stack is drilled and tapped to accept a primary jet then you need that and the main nozzle in order for the carb to work right for either year.

[roonie]

So, yours is an 01A. Look a the pics and your kit. The carb you have is an 85ES and the kit is for an 86ES. Compare the pics I laid out of the two kits. The main nozzle does not come in any kit. That part is essential. The Primary jet used to not come with the 86 kit but I got an 86 kit the other day that had one in it. Fluke, maybe but historically the primary jet is not in the 86 kits. If the jet stack is drilled and tapped to accept a primary jet then you need that and the main nozzle in order for the carb to work right for either year.

Yes my bike is a 85es. Again..on the packaging there was a white sticker label that said 85-87 250 es...underneath that sticker was another sticker that said 1985 250es. The primary jet stack does have threads right at the top. I assumed it was for the new threaded little plug only. I have a main nozzle that came in the kit and the cap to screw on top the main nozzle. Just dont have or see a primary anywhere. not even on my floor..lol. I dont get why they cant send all jets as that is whats hardest to clean. And why not a float to go with the needle...man! I will have to call the honda dealership here in the am and see if i can get the primary seperately. When i called for the carb kit he stated that it was no longer available but that single parts were. I got the kit from an aftermarket type place here in Saskatoon, Saskatchewan for $18. By the way i misinturpreted your instructions and tried to take both the cold start plug and the cold start jet out and broke the jet. Does the cold start jet not come out...if so ..how flyingw? The stem is now broke on it but the bottom is still down there. Im going to see if they have that part seperately too in the am. Any other ideas.....will it work the way it is if i drill it .08mm? Thanks for all your help by the way!

[Flyingw]

Post #3 shows how to get the cold start jet out. Are you saying you broke the cold start jet?

[roonie]

flyingw....can you clarify .....is it the plug that you are prying out that we are drilling .08mm or is it the passage below that plug?In the Honda service bulliten that you posted it states that the cold start jet gets pryed out and an new updated one gets installed...so there must be a jet available..somewhere eh?

1To elaborate on the 85 ES/SX cold start problem I mentioned. This mod only applies to the 85 ES/SX carbs and is really only a problem for you in really cold environments. In a nutshell, because the startup jet metering hole is so small, it doesn't provide enough fuel to fire a cold soaked motor but I'm talking 30deg F or colder. None the less, it couldn't hurt to do this mod no matter where you live. I have attached the original Honda Service bulletin along with pics of how I pry the jet out. You want the modified screwdriver to be about horizontal. Gently push down and the jet should come out. I use a .080mm micro-drill and a Dremmel to drill it out. I have encountered many ES/SX carbs where the startup jet was plugged with debris. You will need a #4 sheet metal screw, a modified flat blade screwdriver and anything with about a 1/4 - 3/8 diameter to lay on the jet stack to act as a pivot. Screw the sheet metal screw in about 1 - 1 1/2 turns. Don't worry about damaging the jet with the screw. The metering hole is farther down than the screw will reach. Pry the jet out, drill it, and reinstall. While the jet is out, be sure to shoot carb cleaner through the hole. If doing a carb rebuild, leave the jet out until final assembly. A set of metric micro-drills can be found at most local tool stores or on the internet for just a couple of bucks.

I have a set similar to these. You will need a Dremmel with a chuck to use these.

http://www.ebay.com/itm/New-15pc-Mic...item2c6e3fee07

[Flyingw]

The metering hole is about halfway down the jet. Without seeing it I can't say whether the metering hole is still intact. Can you post a pic? Those cold start kits are no longer available as far as I know so that's why we are drilling them.

[roonie]

im still not understanding ......when you pryed up with your made up screwdriver with the slot in it, are you taking just the plug out and drilling that plug or did my jet brake in half. In your pic it looks like there is a plug that you pry out and then it sounds like you are drilling either the plug or the metering jet down below....can you tell me which is it? And yes....the lower half of the metering hole is intact. ITs a long way down ...not sure if a pic will show it.

[Flyingw]

ok, gotcha. What you see in the picture is the startup jet. That jet on the end of the screw is what I drill. Down in the hole is another nozzle but I haven't figured out how to get it out to clean it so remove the jet, drill it, spray carb cleaner in the hole and reinstall the jet.

[roonie]

Ok...gotcha.....lol....so the only reason you are taking out the top (jet) is to drill it so as not to contaminate the bottom with filings. I misunderstood and thought the reason to take off the top was to gain access to the (jet ) down below. Like ..why would a person drill something that has been ruined by a sheet metal screw..lol. You may want to insert another short sentence in your tutorial for dummies like me. The Honda bulliten sounds really scetchy...to me anyway.

All ive really done is removed/broke the stem of that lower (jet) ...the rest is still intact.

Now ...what about a primary jet that im missing....will a jet from another year (86-87) or even another machine like a 350 go in my hole and work just fine? Im asking because my Honda dealer may not carry these any longer by the sounds of it. Thanks again for all your insight and quick replies as winter is setting in up here already and I want to RIDE this thing yet.

[Flyingw]

Well the 05A and 10A (350X) and the 04A (TRX250) do not have primary jets so no you can't use a jet from any of those. You will need to find a primary jet. I'm hitting the road in a few and won't be back online till probably late tonight.

[roonie]

Ok...I have what you call the primary jet. I received a primary jet in my kit too. Its the main nozzle with the holes in it that i am missing. Well....my local honda powersport shop does not have this main nozzle i found out today.

[Flyingw]

Ok, that's a problem. I have some carbs inbound but I won't be in town until next week. Search Ebay for ATC 250SX carb and ATC 250ES carb. There is a guy parting out carbs. He may have one listed.

[roonie]

so an 250sx is exactly the same. what other carbs will work flyingw? I did find some carbs in the next province over from me but the guy sounds like that little part that holds an air cleaner down. He wants $50 for a carb...i think...he wasnt too sure..lol what should i be paying for a carb untouched? thanks\

what are the odds of finding a carb kit of another brand that contains this main nozzle?

[Flyingw]

no carb kits have the main nozzle. You need to find an 01A, 02A, 07A, or 08A

[Flyingw]

cost on a carb is all dependent on condition. untouched rebuildable not more than 100.00 but that's entirely up to you.

[roonie]

Hi flyingw....sorry but my pc went for a crap. Anyway...i thought i read somewhere that a honda 300 quad carb would fit these 85 big red 250es....can you advise on these. Also....i know its a long way from your door to mine but if i get stuck looking for that nozzle, would you have one kicking around? Also....what is the # on this main nozzle that i am in need of please flyingw? thanks

[Flyingw]

I'm currently on my way home from a very long road trip. I'll be home Sat evening. Dougpcs sent me some carbs and I bought a few parts carbs on this trip so I think I'll have a nozzle for you. Send me back your Canadian mailing address and I'll let you know what shipping will be. Hopefully not too much shipping first class. Priority will be expensive that I know.

[roonie]

I pmed you flyingw

[Flyingw]

After rebuilding and testing more than two dozen carbs since I started this, I have made some observations about these QA series carbs. Most of the carbs ES/SX have this little skip in step at idle meaning that while its sitting there idling, the motor skips a beat now and then. Sometimes its very subtle and sometimes its very noticeable. I have no explanation for this anomaly.

The other observation is the fall flat on its face when you hit the throttle real hard at idle. Most carbs do this, some don't. I've noticed it more in the 85 carbs than the 86. I have tried an assortment of slides thinking the Teflon coating on the slide is worn but swapping slides out had no effect. I have tried different needle positions, no effect. I have played with the pilot screw adjustment, some effect sometimes but not enough to make the problem go away completely.

Today I loaded up a carb with this problem and moved the airbox out of the way and placed my hand partially over the intake side of the carb blocking about 50% of the opening and the problem virtually went away?????? This leads me to think that when you stab the throttle off idle, it may be ingesting too much air and not enough fuel for that amount of air but how does one go about restricting the amount of air? The reality is that these are not 2 stroke motors and typically we don't stab the throttle on these machines like we do on 2 strokes. They simply weren't designed for this kind of throttle response. My conclusion is, this is something we simply live with. I am by no means a carb expert but I do understand how they work. The book says to warm the engine. Set the idle to about 1400 RPMs +/- 100 RPMs. Turn the pilot screw in until the motor stops then back it out 1 full turn and reset the idle. Any of you guys ever played with this problem and had any success and correcting it? I'd love to hear your input. Even my SX does this but its pretty mild by comparison to some of the others I've seen.

[MojaveRider]

Would a CV style carb like on the TRX300 fix the idle stab problem? In the ES/SX carb, there is the butterly and the slide, and both move directly with the throttle cable if I remember. The TRX300 carb only the vacuum will open the slide, so stabbing the throttle will only open the butterfly and the slide won't open instantly.

I'm no carb expert, just a guess.

I found this cool Youtube video: http://www.youtube.com/watch?v=wyspAHrMbb8

[Flyingw]

I don't think it will. The aftermarket carbs on Ebay are CV style and most of the guys who have bought and installed them have reported problems although a few have reported success with them. The problems range from cable compatibility issues to flat out not running right. I'm going to mess with the synchronization of the butterfly and slide and see if that has any effect. I set the synch per the book so we'll see what I get when I take them out of synch.

[wonderboy]

Hey Flyingw,

I'm also far from a carb expert, but I think this is an inherent limitation on these carbs and the reason why other carbs for different (newer) machines have an accelerator pump. Stab the throttle, and get an extra shot of gas at the same instant. When our machines were brand new and in perfect condition, it wasn't as big of a deal.

As an aside, I had a 200ES carb that just would not idle down reliably. It would hang, oscillate, and do all kinds of bad things. I had the slide re-coated by a company that does piston skirt coatings. Based on measurements, it needed a couple thousanths to fit into the carb body without slop. The results after the coating were dramatic. The idle down (after revving it up) was immediate and solid. Throttle response was hugely improved also, since the pilot circuit which previously had to compensate for extra air leaking around the slide could now be adjusted correctly.

I know the SX carbs have a butterfly too, so this isn't quite as big of an issue on these carbs, but maybe the slide does contribute a bit to the issue. If you want to see more about what I did, have a read here: http://www.3wheelerworld.com/showthread.php/142062-The-fix-for-the-carb-that-just-won-t-idle?

[Flyingw]

You know Frank, that's where my train of thought is going as well and that's why I was swapping slides to see if I could effect the problem. I think these carbs given their age and use are subject to various forms of leakage especially around the slide but the only way I can really confirm this is to find a brand new slide but as I said, this mainly occurs when the throttle is hit hard and fast. Normally with the ES/SX, we don't stab the throttle that way so if someone has a carb the reacts this way its not really a problem if they work the throttle in a normal fashion as opposed to working the throttle like we do on a 2 stroke. If I ever see a new slide pop up on Ebay, you can bet I'll be all over it.

[wonderboy]

In lieu of a brand new slide, you could try refurbishing one. To be honest, I'm not sure which wears more: the slide or the bore in the carb where the slide moves.

With my 200ES carb, I measured the carb slide bore (using a telescoping gauge) and then measured the slide and figured out how much clearance there was. I told the guy who coated the slide how much buildup I needed (If I remember right, I needed a couple thou). We intentionally made it just slightly oversized with the coating. Then I wet sanded it and with trial and error kept checking - sanding - checking and got it so it was a perfect fit. I used a local shop (Dart manufacturing) to do this. Let me know if you want any contact info or help.

[3Wheel_Hunter]

Flyingw,

Thanks for the write up!! I'm rebuilding a 250sx now and am glad to see that I didn't screw anything up. This writeup made me go back and check everything before I reassemble. This write up is better than anything I've read in any of the manuals!

[Chopsaw]

Interesting on the flat spot off idle , because I thought I had a problem with my 85 . I would now agree ,,, that's just the way it is . My 86 has a ES engine , and it doesn't trip off idle . It wheelies very easy , lots of response and you have to be careful you don't end up laying on the ground . It has a KN filter , plus the sock so maybe that riches it up a bit ?

[Flyingw]

I know, Its frustrating. I rebuilt a carb last night and tested today and not a hint of hesitation off idle and its an 85. I'd give a dollar to know what is causing that.

[Flyingw]

Most of you know that Honda offered a mod kit for the 85 ES/SX carbs to fix the cold start issue. Recently I have rebuilt a few carbs that had a different start up jet in it. This different start up jet is what Honda sent in the mod kit. See the pics. The jet on the left is the mod kit jet and the one on the right is the original jet.

MFW, this is what the inside of your carb looked like.

[tri again]

Thanks (again) fw.
I had one that I drained for the winter and it looked like that
in the spring. Non etoh gas and stabil HAD been in there.
Wonder if it's better to leave the float bowl full of the good stuff
contrary to the honda manual storage procedure?..or maybe
fill the bowl with mystery oil?
Wonder what makes 'em fuzzy like that.
Condensation in an empty bowl?

[Flyingw]

That I am predicting is a combination of bad fuel that had water in it. If you want my opinion, for Winter storage, I would drain the fuel from the bowl. Fill the carb with rubbing alcohol and drain X2. The alcohol will flush the bowl and carry away any remaining fuel residue. I would also do the same with the tank but that would entail pulling the tank and swishing some alcohol around in the tank. Drain the alcohol through the petcock and blow the tank out to dry. Then spray a coat of WD40 inside of the tank and seal it up. I would also spray the WD40 through the vent in the cap. I'm not a big fan of Stabil. I too have had carbs that looked similar after using Stabil. I think a dry carb and oiled tank is the way to go.

[MFW]

Wow, that is a hot mess! I am crossing my fingers you can make it new again.

MFW

[kilabeez0]

wow this thread was bumped today what a coincidence. Just wanted to say thank you for this write up. I cleaned my carb out 2 years ago and ever since putting it back together if I stabbed the throttle it would just bog out. Well I finally got around to taking it apart this afternoon thinking a piece of gunk was just clogging up a hole. Well after looking at your pictures I realized I had put the primary #45 jet and the main jet #130 in each others spot. So it should be noted that both of these jets have the same size thread and can fit in each others holes! I need to clean my gas tank out before I put it back together but I'm sure it'll work fine.

2 quick questions. My carb didn't have the vent tubes just pointing at the ground separately, mine had them connecting with a t connection or something odd and the tube then ran up the neck of the trike. Any idea why?

Second thing is half of my pilot screw is snapped off. Ive never removed it and I dont see it being an issue. Should I just leave it alone?

Ok one more thing. What size fuel line is this 5/16?

Thank you for the write up!

[Flyingw]

The 86 carbs came with the spaghetti mess of a vent. They routed both vents in to one. It kinda sucks!!!!! When I rebuild the carb, I go with two simple vent hoses. The reason is, if the two in to one becomes clogged by mud or something like that then you have no flow but if you have two independent vents, you can lose one and have the other. Just playing odds. You always need air above liquid to flow properly.

If your pilot screw is broke and the carb is operating ok, leave it alone however if you want to remove it, cut a slot in the screw with a Dremmel. Its ok if you cut in tot he sides of the pilot screw tower. You just need it deep enough to put a screwdriver blade in to so it can be turned out. Be sure you remove the flat washer and oring that are under the spring.

The fuel line is typically 1/4 but 5/16 works too. Good luck.

[kilabeez0]

My trike is an 85. Wonder why the vents are like the 86 unless someone swapped it out. How else can I tell if it's an 86 carb? Thanks!

[Flyingw]

Look at the number stamped on the rim of the bowl under the fuel hose nipple.

QA01A 85 ES
QA02A 85 SX
QA07A 86 ES
QA08A 86 SX

[Flyingw]

Hey MFW, I got the choke valve out. I combination of heat and candle wax did the trick. Luckily the tabs on the valve were still intact so I hooked the cable and slipped a collar over the tabs to keep them from opening. Pulled on the cable and I got it to move up. Tapped it back down. Hit it more heat and got it to move up again. From there I exercised it up and down a couple of times and out it came. I first tried soaking it with Teflon liquid but it wasn't going past the frozen oring so that was pointless.

[KingPaul]

FlyingW, I sent you a "Private Message" but am not sure if I did it correctly. First off, FANTASTIC step by step "How Too" & thank you so much for the detailed information. I took everything apart one jet by one jet but for some reason I can't get the Primary jet to go back in even without the emersion tube. Any thoughts as to what I did wrong? I started with the main jet, went to the start up jet, and then took out the Primary jet. I'm new to this but I've already rebuilt my 86 sx without any issues.

Thanks for your help with the rest but this doesn't make any sense to me

KingPaul

[Flyingw]

My apologies Paul. You did send that and I spaced it. You are installing the immersion tube skinny end first right? Also, is the immersion tube pushed in as far it would go? The nipple end of the tube should be sticking up in to the venture of the carb..

[KingPaul]

No problem, I'm going to work on it again tomorrow as it's raining here in the beautiful Garden State and I won't be getting home until late. I think I know what I'm doing wrong and am a little embarrassed to admit it but I will let you know. Let me know if you want the carb parts I have.

Thanks

KingPaul

[Flyingw]

Don't be embarrassed! I've had my fair share of bonehead mistakes over the years. I will take the carbs if you have no need for them. Let me know what the shipping is. Ship to:

James Baldwin
14712 SE 77th St
Choctaw, OK 73020
405.420.1114

Feel free to call me anytime. Jim

[acellr8]

Great thread and Thank you for taking the time to post this up! I used it to rebuild the carb on my 250ES and it now runs like it should after 5 months of dying out on wide open throttle. Great pics and step by step. Much Appreciated!!

[Flyingw]

You guys are most certainly welcome. Some of us can read and completely understand but if you're like me, you need pictures to confirm what was just read. I have had nothing but positive feedback on this little thread so I'm very pleased you guys have found the information useful. I'm always here if you need help and I do have a ton of spare carb parts so speak up if you need anything.

[dreux13]

Hey Jim, this write up is a life saver and I now have the ability to disassemble from the SX, rebuild and have ready to ride inside of an hour! I followed it from the beginning and did have to rebuild it three times due to bonehead mistakes. Just to save someone else time, here's what I did wrong...

1st shot, I had the float baffle bell housing installed upside down preventing the float from moving...doh! Second, I did the same thing that kilabeez had with having the main and pilot jets swapped! The machine idled and ran up to 1/4 throttle perfectly each time and then fell on its face mid range. I went nuts trying to figure out the problem, but I eventually figured out the jets were reversed. She now runs great!

Lastly that gasket in the oven trick was awesome! Worked like a charm....twice!

Thanks so much!

[Flyingw]

That's great!!!! Is there any part of the tutorial that needs work? Clarification? more explanation? The oven trick with the bowl gasket trick works almost every time. Of the gasket is old and dried out, it usually won't work.

[dreux13]

I think just pointing out that the main and pilot jets do fit in to each other's spots and to make sure you don't have them mixed up.

I was using to forum to troubleshoot and found at least 10 threads with people that had the same symptoms I had but never posted the ultimate fix. I'd bet money they had those two jets in the wrong spot and we're too embarrassed to say something! Some ended up getting a replacement carb!

Thanks again!

[mayhem17]

This is a great thread that was linked to me today because I am having issues with my 85 250sx carb. When I got the bike it wasn't running. I installed a Moose carb rebuild kit right when I got it. I have ensured that everything is clean and in the correct spot. The issue I'm having is off idle, if I stab the throttle quickly, it falls on its face and sometimes dies. If I roll onto it, I do not have the issue. Starts and idles great. 130 main and 38 pilot I believe right now. (all stock jets) Motor is stock, uni filter with complete closed airbox. It seems to run great once I get about 1/4 through the revs. Had been told to also check my float level which was great. I'm at 1900 ft elevation here in Oklahoma. Days are running about 90 degrees right now, although it did the same when it was 50. Would you simply suggest getting a bigger slow jet? I've screwed in the air screw abou 1/2 turn from stock, didn't notice much of a difference. Any help here would be appreciated. Thanks.

[Flyingw]

This is a common problem with these carbs. I'd say more than 75% of the carbs I've rebuilt including my own does this. I have gutted carb bodies and put in completely different parts including the butterfly and slide linkage assemblies and the problem didn't change at all. I've tried different jets and moving the needle up and down and still the problem persisted so I'm at a total loss as to the cause. Like I said, some do it, some don't so all I can offer is... Don't stab the throttle like you would on a 250R.

[mayhem17]

This is a common problem with these carbs. I'd say more than 75% of the carbs I've rebuilt including my own does this. I have gutted carb bodies and put in completely different parts including the butterfly and slide linkage assemblies and the problem didn't change at all. I've tried different jets and moving the needle up and down and still the problem persisted so I'm at a total loss as to the cause. Like I said, some do it, some don't so all I can offer is... Don't stab the throttle like you would on a 250R.

Do you have any suggestions for a replacement carb with an accelerator pump that works well for the 85 sx? I'm thinking that it would solve my issue. I've heard they make them fairly cheap also.

[Flyingw]

No I don't. I recently rebuilt a TRX300 carb and tested it on my mockup and it ran fairly well considering the jetting was off. The 350X carb is an upgrade but its basically the same carb as the SX/ES carbs. I know the Chinese carbs are hit and miss so I'm not sure what the right answer is for a more advanced carbs would be without having a sample for trial and error.

[barnett468]

No I don't. I recently rebuilt a TRX300 carb and tested it on my mockup and it ran fairly well considering the jetting was off. The 350X carb is an upgrade but its basically the same carb as the SX/ES carbs. I know the Chinese carbs are hit and miss so I'm not sure what the right answer is for a more advanced carbs would be without having a sample for trial and error.

Hello flying . . I don’t know if you have seen what I have posted on his spark plug thread for him but I basically suggested he try a carb with an accelerator pump . . I also suggested he run it by you to see if you had any ideas for one . . I only came up with two . .one is a Chinese flange mount 30 mm one and the other is a 33 mikuni flat slide . . I know the sx carb is a 27 mm and the trx250x carb that damon suggested to me when I asked him if he knew of any, is a 36 mm, so as I was looking at fcr carbs which are 35 mm at the smallest and need the accelerator pump jet changed to tune out their inherent flat spot if you get one, damon mentioned the mikuni tm33-8012 carb to me . . although it is considerably bigger, as long as the hole in the carb boot or head is only 33 mm, it will function similar to a smaller carb, however, the biggest prob is the height of the throttle cable mounting bracket and of course the intake boot, which im guessing mikuni would have . . anyway, I was curious as to whether you knew by looking at the mikuni below whether the bracket would interfere with anything or not . . also the air box boot might not fit right.

Heres the link to it

http://www.ebay.com/itm/Mikuni-33mm-Accelerator-Pump-Flat-Slide-Performance-Carburetor-TM33-8012-/171644978572
http://i.ebayimg.com/00/s/MTYwMFgxNjAw/z/4i4AAOSw~OdVX6go/$_57.JPG


Heres the Chinese 30 mm I posted for him which will definitely require a cable mod, plus the cable goes in the top of the carb so I don’t know if there would be an interference fit with this one either . . a mounting adapter could easily be made.

thanks in advance for any suggestions.

.................................................. ..........http://i.ebayimg.com/00/s/NTAwWDUwMA==/z/~iMAAMXQuCdThqok/$_12.JPG

[barnett468]

.
I found a few things today in my search to adapt the 30 mm carb I posted to the 250sx.

This adapter may bolt right on to the 30 mm carb I posted which may actually be a 27 mm instead . . The other end has a 61 mm bolt hole spacing and 30 mm bore size . . unfortunately I can’t tell if either set of mounting holes is offset but this should be able to be made to work . . from the othr hotos i hve seen, it also looks like it is clocked correctly, however, I am still looking for others . . I started off with the old Honda cb 175 and cb 200 ones unfortunately the 175 ones were for 20 mm carbs and the 200 ones where clocked incorrectly so the carb would be rotated too much.

...............................http://i01.i.aliimg.com/wsphoto/v0/32249875141_1/Motorcycle-Dirt-Bike-Racing-Carburetor-font-b-Carb-b-font-Aluminum-Adapter-Inlet-Intake-font-b.jpg


1983 - 1985 atc200x throttle cable should thread into the atc250sx throttle housing and be long enough to reach carb . . inner length may need to be adjusted.

.................................................. ...............http://i.ebayimg.com/00/s/MTYwMFgxNTU5/$%28KGrHqV,!n0E-v2loRWhBPutmd4IRw~~60_35.JPG

[Flyingw]

Good job on the research. Space is defiantly a consideration. The headroom above the carb is not very much to allow a cable to come in through the cap unless it had a 90deg fitting on it. The left side of the stock carb has the airbox tube running next to it. Several years back I did up an 81 XL250S and it had carb with an accelerator pump. A possible candidate...

Sizing a carb for any given motor can be tricky for sure so trial and error is about the only thing we can do at this point. The stock carb at idle is running on the pilot circuit of the carb. The slide is down and the butterfly is closed. Fuel is being supplied by a hole in the venture outside of the butterfly. As the throttle is opened, the slide and butterfly open proportionately at the same time when the two are synched. As the throttle opens, fuel is delivered by three different circuits pilot, slow, and main jets. All three circuits have to work together as fuel is handed off from one circuit to the next. When the motor is idling and the throttle is stabbed, fuel goes directly from the pilot circuit to the main circuit but from what I've seen testing carbs on my mockup, there is a pretty good amount of fuel blowback that happens. I tend to think the problem when the throttle is stabbed, it injects an excess amount of fuel in to the venture which briefly floods the cylinder. Some of the QA series carbs like the TRX250 and 350X do not have a primary jet. I have tried the TRX250 on my mockup and it will only run when I take my hand and block off about 50% of the opening. When I do that the carb actually runs pretty good. That tells me the airflow in to the carb with its stock airbox restricts more airflow over the ES/SX carbs. The 350X carb is the same body without the primary jet but bored larger in the venture and slide. The X carb runs pretty good on the SX motor but its a bit fat on the top end.

I have seen the good, the bad, and the ugly with all the carbs I've rebuilt. There have been some that were so crudded up that I thought no way will it run right but it did. On the flip side, I have two carb bodies (1 ES and 1 SX). The ES carb is in absolutely beautiful condition but it will not run worth a crap at idle or slow speed. The SX carb runs beautifully from idle to mid throttle but at full throttle it blubbers badly. Both of these carbs I have soaked, cleaned and blew air through all holes and they blew clear. I did find on both of them the vent holes that are under the cap, the two that have the brass inserts were blocked. I thought I had that AHAAA moment. I cleared the blockages and I was positive that was going to fix both.... Didn't effect the problem one bit on either. I have swapped out every single part on both carbs and nothing I did effected the problem. The problems with both carbs remained unchanged so the problem has to reside in the bodies but what baffles me.

The stabbing problem I thought could be a worn slide. The slides have a Teflon coating on them and they are subject to wear but changing slides had no effect. There is a procedure in he book for setting the pilot screw and there have been a few that did fix the stabbing problem by adjusting the pilot screw per the manual but every motor breaths differently so even if I tune it out on my mockup doesn't mean it wont do that on the intended motor so I always send the carb back with the number of turns outlined in the manual. The problem exists on all year ES/SX carbs. I have played with needle clip position with no change in the problem. I am by no means any kind of a carb expert but the way I rebuild these QA series carbs seems to work great with the exception of the ones that have the stabbing problem but even those run just fine if I don't stab the throttle. Another intermittent problem is commonly see is the "skip in step" when its idling. Its as if the ignition shuts off for a fraction of a second and then restarts. Its just a frequent hesitation at idle.

SO, that's what I know at this point. Surely there is a carb out there that would work as a suitable substitute but which one has yet to be identified.

[250rRoostmaster]

My little lifan 125 in my atc70 did the same thing. Huge bog from idle if you stabbed the throttle. Came stock with a 30 pilot. I ended up at a 52.5 pilot which seems crazy since most people run a 20 and have great results. But the big BOG is a Lean condition rather than rich in all my tuning experience. A sputter is rich. I'm not disagreeing with Flying W in any way, just throwing my experiences in. All motors run differently. Have you tried going way up on the pilot to see if it helps?

[mayhem17]

217048

So, I took it apart once more last night, and realized that I've never had this baffle in my carb... Will this cause an issue? I have another carb that may have one (haven't busted it open yet)

[barnett468]

217048

So, I took it apart once more last night, and realized that I've never had this baffle in my carb... Will this cause an issue? I have another carb that may have one (haven't busted it open yet)

That's basically a splash shield that helps keep fuel around the main jet while riding on rough terrain.

Did you do a compression test yet?

[barnett468]

.

oops, to answer the rest of your question...no, it will have no affect on your existing hesitation problem.

[Flyingw]

My little lifan 125 in my atc70 did the same thing. Huge bog from idle if you stabbed the throttle. Came stock with a 30 pilot. I ended up at a 52.5 pilot which seems crazy since most people run a 20 and have great results. But the big BOG is a Lean condition rather than rich in all my tuning experience. A sputter is rich. I'm not disagreeing with Flying W in any way, just throwing my experiences in. All motors run differently. Have you tried going way up on the pilot to see if it helps?No I haven't but that has been rolling around in my head.

[barnett468]

.
Flying, thank you very much for the highly detailed info and the time you put into it . . I’ll just post some general info and try to be brief . . I know you’re a sharp guy and likely know some, if not all of what I’m posting below, so it’s mainly for some others whom might at least find it interesting if not helpful . . I am also aware that you know this particular style of carb very well which is why I have referred others to you when I saw they had a carb issue with one, so none of this will be about me making suggestions to tune this particular carb, especially since I don’t know this particular carb well, plus you have already been there and done that.

Some of the info will also be irrelevant to most because people are simply not going to change some of the things I mention just to try and reduce the hesitation their engine has which is understandable, so again, some of it is mainly for general informational purposes . . I know that El Camexican is also familiar with some, if not all of the info below, so I’m a little surprised that he hasn’t made a post on the op’s thread at the very least, but I haven’t seen him post much lately so maybe he just isn’t around . . I am also not the most knowledgeable person in the world on these subjects, however, I at least know enough to get by and where to go if I need more info.

None of the mfg’s are dummies, but on occasion, but all of them, including Kawasaki, have built something that has had one type of quirk or problem in the past, therefore, none of this is to rag n Honda…too much, lol . . Problems like this just happen sometimes . . The mfg’s certainly learn from their mistake and eventually fix them on future models.


CAMSHAFT

A cam that has a lot of overlap will idle poorly due to low engine vacuum and a “dirty” intake charge that is diluted and contaminated by exhaust gases that haven’t been completely evacuated from the cylinder, therefore, one of my guesses is, that with this particular bikes combination of ex pipe and ignition timing and compression etc, the cam has too much “overlap” . . Camshaft lobe overlap is affected by a few factors, one of them being the distance between the cam lobes which is referred to as “lobe center angle” or “lsa” for short . . Most stock automotive engines have lsa’s in the 115 to 116 degree range . . This is to make the engine idle smoothly and be more “streetable” with good throttle response, especially in traffic etc . . Most performance automotive aftermarket cams use a lsa of around 110, which is a huge difference . . If all other things are equal on a cam, the one with a lsa of 116 degrees will idle far smoother, and have far more engine vacuum and better throttle response than the cam with a lsa of 110 degrees.

I would be interested to know what the amount of overlap the 250sx cam has compared to another 250 cc engine that didn’t exhibit this problem which has a non accelerator pump carb . . If the lsa was increased on the sx cam, the hesitation would be greatly reduced if not eliminated if it had a properly working and tuned carb, but that’s going to affect the power characteristics, plus changing a cam is not what most people would want to do to improve this problem.


ENGINE VACUUM

The more vacuum an engine has, the better throttle response it will have and the easier it will be for the engine to draw fuel from the carb . . I would be interested to know what the vacuum level is on these engines at idle and when the throttlke is stabbed . . the stabbing test is not a definitive test due to some variables but it still might yield some useful info . . One just doesn’t know unless they try it . . If the vacuum at idle or around 1/8 throttle is less than around 14 hg, an engine can start to exhibit carb related hesitation and or poor idle characteristics.


CARBURETOR SIZE VS ENGINE VACUUM VS THROTTLE RESPONSE

In general the smaller the carb, the higher the vacuum will be . . It is possible to run a 40 mm carb on a 250sx and have it not work much, if any worse, than the stock 27 mm carb providing the intake tract size is reduced sufficiently . . This gets a bit complicated and it will reduce power but it will still work . . this concept is exactly the same as the restrictor plates that Nascar occasionally uses . . To this end you could get a piece of pcv pipe that will slip snugly into your carb adapter or the exit side of the carb and see what affect that has on throttle response . . you can also check the engine vacuum before and after . . Of course you would need t rejet your carb and obviously this will reduce peak power but it might still give some useful info, and if it does significantly reduce hesitation, and someone uses the lower end of the operating range most of the time, it might be a viable solution to their hesitation problem.


IGNITION TIMING

If an engine has insufficient amount of timing it will have both a hesitation and will spit back out the carb . . This is easy to test if someone wants to . . Just reduce the timing on your engine by 10 degrees and check it out . . With this in mind, I would look at the ignition pick up and see if it can be easily modified to advance the timing by 4 - 6 degrees . . This amount is definitely enough to alter the performance enough to feel, however, it’s not what could be considered excessive . . If this reduces the hesitation and the engine doesn’t ping, it seems like a simple, partial cure.


EXHAUST SYSTEM FUNCTION AND DESIGN

In general, the exhaust pipes are not just a way to route the exhaust gasses to the rear of a vehicle, they are also intended to perform a function called “scavenging” which basically creates a sort of vacuum effect that actually helps pull the intake charge into the engine . . This affect is more pronounced on vehicles that have multiple cylinders with individual pipes that converge/merge together at the end where they exit into one single large tube . . In fact here’s a couple short, super low budget, simple tests, that visually shows the vacuum affect created by exhaust scavenging.

https://www.youtube.com/watch?v=pDQXsfeZGwk

https://www.youtube.com/watch?v=yMyKv_P80eI

https://www.youtube.com/watch?v=W7lbTcdaYpE


CARBURETOR SIZE

Based on all the info you have provided along with other info gathered, it is my guess that to reduce the hesitation, it is best to stick with a carb that is between 25 and 33 mm for this particular bike in box stock form anyway . . There is an oval bore Chinese pumper carb with a 27 mm outlet which would make it around a 25 mm carb . . The one I posted earlier was claimed to be a 30 mm but that might have been the outlet size . . If it is, then that carb is around a 27 mm . . It’s a bit hard to tell the true size of some of these because the sellers don’t always post the exit size and instead often just state a mm which in many cases I have seen is incorrect . . Either way, these seem to be in the correct range for this purpose.


THROTTLE RESPONSE TEST

Posted a few posts above this one.


LEAN CONDITION TEST

Posted a few posts above this one.


CARBURETOR HEAD/TOP CLEARANCE

That’s a very good description . . I will look for a top that might have an elbow on it, there are some . . Another option is to have the end of the cable modified by having an elbow installed . . If you look at the bike below, it looks to me like it might have a Mikuni on it . . I have no idea if they used an elbox on top of the carb though . . The carb is also mounted square to the ground . . I don’t remember if the 250sx carb is mounted at the same angle or if it is angled upward . . Either way, if the carb used, is angled upward, it would have a little less bend in the cable which might make it a little easier to use a straight cable on it . . You would certainly be one of the best judges of that since you are very familiar with how much head clearance they have for the carb.


CHINESE CARB QUALITY

I for one am not a fan of Chinese made parts in general, however, of the posts I have read regarding the Chinese made carbs, most were positive . . There were a few that were initially negative, however, it was later determined the either the float level was off, or the needle had debris that came from the persons fuel tank stuck in it etc . . I’m sure some of them simply don’t work well for some reason or another, but judging from what I have read, in the majority of the cases they seem to work just fine . . If I remember correctly, they may not use the exact same jet numbering system the Keihins use but regular Keihin jets work in them.

Also if I recall correctly, Damon told me that some, if not all of these carbs, are the exact same model that are used on some production Chinese motorcycles, therefore, in light of that info alone, I would guess that they should be fairly decent considering there are around 100 gazillion motorcycles in China but that’s just my guess.


ACCELERATOR PUMPS

Just buying a carb with an accelerator pump does not mean that is going to work better without being properly tuned . . One of the complications with carbs that have accelerator pumps is that one size does not fit all . . in other words, the pump may squirt too little fuel or too much . . it may also not squirt fuel long enough or it may squirt it for too long, and unfortunately, unlike the accelerator pump on most if not all aftermarket automotive carburetors, the pumps on a motorcycle carb are rarely, if ever, adjustable . . This means that if the pump on the carb needs some adjustment, you will likely have to modify or make some parts to do that with.

One example I heard of regarding problems with accelerator pump carbs, was related to the Keihin FCR model . . The problem is apparently so common, that Boysen makes a $120.00 kit with an adjustable jet to cure this with . . I read on the net that one guy was smart enough to simply buy a $5.00 jet the size he needed to fix this prob on his carb.

The point being, don’t expect any carb with an accelerator pump to have the pump setting be ideal for your bike right out of the box . . You might get lucky…you might not . . This being said, I’m guessing [hoping] that the ones on the small Chinese carbs will be pretty close for this particular app at the very least.


Please feel free to mention any errors . . I have no edit button so once it's posted I can't correct it.
.

[barnett468]

.
ok, I went window shopping today and eventually came up with the items below . . I started thing about hesitation off idle and suddenly thought about constant velocity carbs like the original 750 hondas had so even though they were not considered a performance carb at the time, I still figured that it would at least reduce or eliminate the hesitation when the throttle is stabbed simply because the slide will not open until the engine has sufficient vacuum so they are a great carb for people that have an engine with this type of prob but don’t have the self control to keep from stabbing the throttle.

well during my search, I not only cane upon standard cv carbs, I also came across some that have an accelerator pump so what the pump does on a cv carb is force some fuel into the engine so it builds revs faster which increases vacuum which in turn opens the slide sooner than a cv carb without a pump so there is far less delay between the time you open the throttle and the time the slide opens . . not only this but these are spigot mount like the factory 250sx carb . . if they are a hair too big for it then just buy a a bigger carb mount from mikuni for $15.00 . . they also sell ones with a 15 degree downward bend if needed . . but wait…theres more, as an extra added bonus, it has a side mount throttle cable so the concern for headroom is no longer there…oh, oh…and they are only $57.00, but hurry while this limited time offer lasts . . the stock 250sx cable might also work.


this should be 30 mm bore with actual 27 mm flow oval bore . . it looks like it shows two different throttle cable bracket types . . contact to confirm if interested . . $57.00

http://www.ebay.com/itm/Chinese-Go-Kart-Cart-Performance-Carburetor-Carb-3mm-gy6-150cc-Intake-/261912361112

http://i.ebayimg.com/00/s/NjQwWDY0MA==/z/s2QAAOxyThVTZFrK/$_12.JPG
Heres a couple more

gy6 250 and cf250 cv type no pump

http://www.ebay.com/itm/KEIHIN-30mm-Carburetor-For-GY6-250cc-CF250cc-Water-cooled-ATV-Go-Kart-Scooter-/111539386490


gy6 cv type with pump fits 150 cc

http://www.ebay.com/itm/Keihin-Carburetor-CVK30-fits-150cc-big-bore-Honda-GY6-motorscooter-engines-/221449096781


Ok, here’s what I have so far on carb top elbows . . The tops on both of these look like they will fit the 30 mm carb I posted, plus they are all Keihins so the thread pitch etc should be the same . . Of course the atc125 carb top is discontinued so to get one, a person would have to buy a complete orig carb or a Chinese one . . The tops could be swapped and the carb the top was scavenged from can probably be resold on Ehay fairly quickly for 1/2 price.

This elbow may cause the inner cable of the throttle cable to be too short . . If it does, a new inner cable can easily be made.

Original Atc125 carb

http://www.ebay.com/itm/like/361187470082?lpid=82&chn=ps

http://i.ebayimg.com/00/s/NDgwWDY0MA==/z/ceIAAOSwm8VUuNsa/$_35.JPG?set_id=880000500F


Chinese carb

http://www.amazon.com/Carburetor-1979-85-1984-85-ATC125M-1980-86/dp/B00AWBNQ0I
http://ecx.images-amazon.com/images/I/41YD%2BvZGfSL._SY355_.jpg

[barnett468]

.
ok i can see that the cv carb has two different locations the cable could be mounted . . the rear cable mounting bracket could be removed to reduce weight and enhance its beauty.

[barnett468]

.
at least i think that might be whats going on . . a little hard to tell for certain


i have no edit button

[Flyingw]

Boy Barnett, when you get after something, you get after it. Interesting prospects and I appreciate all your efforts. What I would like answered is why do some of the stock carbs stall on stab and some don't. What is the common denominator? There are lots of stock ES/SX carbs out there on our beloved machines and I would guess that most of the owners would rather just stick to their trusty old QA series carb including myself. I'm not saying that identifying a suitable replacement is just as important because it is but for those carbs with the stabbing problem finding a solution to correct the problem as inexpensively as possible is what I would like to focus on at this point. Reason being with the steady amount of carbs I do, when I rebuild a carb with the stabbing problem, I would like to apply the fix during rebuild and return a perfectly operating carb to its owner is my goal. I would like to gather a systemic plan to troubleshoot and identify the root cause of the stabbing problem. Could it be something as simple as changing a jet size or even looking at the linkage to see if that has something to do with the problem. At this point I think going back and starting over is the way to go but I need a carb identified with that problem to be used stickily as a control specimen so if anybody has a carb they would like to offer up that has that problem and the more severe the better would be greatly appreciated. It wouldn't be to keep it but simply to borrow it for troubleshooting.

Don't stop what you're doing Barnett as that information is valuable and who knows. You may just find the perfect replacement carb. Those Chinese carbs sold on Ebay have had mixed results mostly bad. I've had guys tell me they bought one and with everything they did, could not get the motor to run right among other issues like cable fitment but some have reported the carbs worked perfectly so that has me baffled as well. Anyway, keep on with your research. If anybody reading this has anything to contribute please speak up. The question is.....what is causing some ES/SX carbs to stall when the throttle is stabbed at idle?

[barnett468]

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lol, yeah, im one of those that doesn’t accept failure providing it makes sense to continue on to find the problem . . as john lennon once said. There are no problems…there are only solutions.

I understand your focus and your goal and im with you that it would be nice to find the prob and be able to keep the bike original, but I can only throw random suggestions at you at the moment and it would require a lot more detailed info to maybe narrow the cause down . . it would also help to have a carb in my hand to see what they did but obviously that’s not practical . . I did notice your post earlier that you said you had not tried to go big on the pilot to yet to see if that would help . . unfortunately I haven’t had time to read thru your entire thread so other than that comment, if its correct along with the others you posted in your reply to me is all I know that you have tried.

I guess one question would be why haven’t you tried a big pilot to see if that helps?

I know you said that you though one might be rich because of it spitting back and if everything else was in perfect shape as far as compression and timing etc goes, that certainly sounds to me like the most likely cause but with an unknown cause like this, there is little I would rule out.

I though you said that your carb also did this so if that’s the case, then why don’t you experiment on that? . . I know that seems like the obvious thing to do so im guessing there is obviously a good reason.

I would guess that unless your bike ever ran without a hesitation that it would not be a good candidate to use but I would guess that you probably had tested other sx carbs on there that did work well so I really have little to suggest at this point especially with all the unknown factors.

The dream situation would be to have an nos bike or close to it so you have an ideal baseline but since that’s obviously not possible, just having a bike that does run good is the next best thing to test a carb on . . its obviously a matter of eliminating as many variables as possible.

For starters, I would slam a big pilot in a known problem carb just to see what it does . . yeagerb actually suggested that to the op of the spark plug thread whom is also the one that posted the carb question for you earlier . . it is unknown if his bike ever ran good while he had owned it so that part is not a help and he has not yet tried a bigger pilot jet, so hopefully he does and hopefully it fixes it and hopefully that is the cure for all carbs that have this problem.

As to why one carb does it and another doesn’t if they are both jetted the same and the slide and butterfly are both timed the same would suggest to me that it might be caused by casting flash in passage most likely an air passage like one of the ones in the carb throat but that seems unlikely to me but until the cause is determined, anything is possible.

Also, if this problem is really huge, I would think that it would have been resolved thru warranty when the bike was new because I cant picture someone buying a brand new bike and having a huge problem with it and not having honda correct it and if this is the case, it seems reasonable to guess that none of these had a huge problem because it should have been fixed . . if one assumes this, then it seems reasonable that something has changed in the carbs that have this problem and if worn parts are eliminated as a cause and all the jets are clean etc, it seems that it would point to a partially blocked passage again and in the ones in the throat of the carb don’t have removable jets, it’s a bit hard to tell with those . . if there are plugs on the outside of the carb for some of the other passages then these could be drill out and replaced after the passage is inspected etc.

As ridiculous as my wd40 test may sound to some, I can assure the doubters that they do often yield valuable info . . not all tests need to have $10,000.00 worth of scientific equipment to be useful so I would actually try that on the next one . . as you obviously know, you really need to determine whether its caused by a lean condition or a rich one first.

Another one you could try that may or may not yield useful info is a to take a timing light and connect it to the bike and point it at the carb throat in a fairly dark room and you should be able to see if and when the carb is getting gas . . at the very least the effect is fun to see . . but I can tell you that this is a good diagnostic tool for checking the accelerator pump action vs the time the fuel begins to flow out of the boost venturis . . I actually had a video of this showing an engine that bogged because the accelerator pump quit delivering fuel before fuel was drawn from the boost venturis which is a common prob with big cam engines because they have low vacuum at low rpms which is what I mentioned in my earlier post.

I would love to have a bike and a few carbs to toy with because I like solving problems like this . . I do it often on automobile engines because I build a lot of those and repair and restore and sell old muscle cars for a living . . if I lived near by and you had the bike and carbs I would be more than happy to come over and try to help if you wanted, but I really think that with a known bad carb and a known good one, and some spare time, which is hard to come by for many of us, im confident that you will figure this out on your own, but im certainly more than happy to keep making some type of suggestions if you want but I would give the bigger pilot a try to start with as yeagerb and someone here also suggested.

[barnett468]

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well this makes little sense, but theres probably more, lol.

"I know you said that you though one might be rich because of it spitting back and if everything else was in perfect shape as far as compression and timing etc goes, that certainly sounds to me like the most likely cause but with an unknown cause like this, there is little I would rule out."

should read

I know you said that you though one carb might be rich because it was spitting back when you stabbed the throttle, and if everything else was in perfect shape as far as compression and timing etc goes, that certainly sounds to me like the most likely cause but with an unknown cause like this, there is little I would rule out.

yup...still aint got no edit button.
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[barnett468]

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oops..."thought" not "though" . . ok, guess i better go to sleep

[mayhem17]

That's basically a splash shield that helps keep fuel around the main jet while riding on rough terrain.

Did you do a compression test yet?

Have not done a compression test on it yet, didn't feel that I needed to. Has plenty of resistance on the kicker when I kick it over, and starts / runs great with no smoke or issues with power.

[barnett468]

Have not done a compression test on it yet, didn't feel that I needed to. Has plenty of resistance on the kicker when I kick it over, and starts / runs great with no smoke or issues with power.

Ok that’s good but on my bikes, I have a file for each one and noted everything I did and the approximate hours on it so I have something to look back at if I need to . . In your case, I would do a compression test even if it was a brand new bike . . One reason for this is that if it starts to run bad later on, I can take a compression test and easily, instantly see if there is a problem there or not . . Plus it will give me a rough idea of how fast it is wearing out.

The more compression you have, the more engine vacuum you will have, which in turn increases throttle response [reduces hesitation]throughout the entire rpm range . . Increasing compression will also increase throttle response because of the increased power the higher compression gives it, and both this increased power, and increased throttle response, will be throughout the entire rpm range

[longbedGTs]

Thanks for the writeup and pics! I'm rebuilding the carb for the 2nd time on my '85 350x due to a problem with it only running with choke full and halfway on. Choke off, it won't run. I found that the pilot screw didn't have the oring in the proper location...it was in the "groove" where you specifically said there shouldn't be an oring there. Thanks for that info! Also, mine doesn't have a main nozzle or primary jet. The hole for the main nozzle isn't even drilled through into the main air passage and the hole for the primary jet isn't threaded, so...not sure what to think about that. I hope it will run like it should after finding this "problem". Thanks again!

[Flyingw]

You are correct Longbed in that the 350X does not have a primary jet. Neither does the QA04 or the QA09 (TRX250) so just ignore that. Usually when a carb wont run with the choke off, there is a jet that's plugged but it could also be a vent that's plugged. If you look under the cap, on both sides of the slide there are four holes, two large and two small. The large ones are the vents for the bowl but the other two are the vents for the passage ways that feed fuel through the various circuits of the carb. Be sure to spray carb cleaner through those holes and blow them out real well. I have tossed a few carbs because those passageways were blocked and no good way of reaming them out othr than drilling the brass plug balls they put in after the passages are drilled. Just know, every hole should blow through to somewhere else so do the best you can to clean them out. I have X carb bodies if that one fails to work right. Is it an 85 carb or 86? Look on the rim of the bowl under the hose nipple QA05 is 85 and QA10 is 86. It does make a difference when you install a rebuild kit as the slow jet is too small for the 86 carb.

[longbedGTs]

It's an 86 carb...and this is news to me! 3 of those 4 holes are clear, but one of the smaller holes(the one that doesn't have the brass piece) is stopped up. I straightened a paperclip and put it in until it bottomed out, but that hole is still plugged. Is there another angle I can go through it at?

*edit* I followed this passageway going by the casting and it appears to "empty out" into the hole that the primary jet would have been if it were equipped. So am I correct in assuming that this hole is not used since the primary jet is not used? Also, rebuild kit came with a 42 slow jet(used a 42 in last rebuild also) but looks like this is too small and will need a 38, right?

[Flyingw]

Are you referring to the vent hole? If so, yes that vent hole is still used but it changes direction at the bottom of the vertical hole. The vertical hole dumps in to the passage that runs from front to back. If you look at the front and back of the venture, you'll see holes on both ends. That horizontal passage also feeds the choke valve hole so blow through every hole you can find.

As far as the slow jet, the 42 jet is too small for the 86 carb. Reuse your old jet #45. If you use the #42. it will be too lean at idle. I about smoked a rebuilt motor. Initial engine start, it idled about a minute before my head pipe was glowing red. That's when I learned the difference between the two carbs and the rebuild kit.

[longbedGTs]

I've added a picture with the arrow pointing towards the hole in question. Ok...looks like I need to get a 45 slow jet then. I don't have the factory jet because I must have thrown it away when I did the last rebuild(using the 42 jet). Also, the main jet is 138. Is that ok? Uni filter in stock airbox and DG full exhaust, otherwise stock.

226651

[Flyingw]

My bad, that hole is not drilled on the 86 carb. As far as the main goes, that's all dependent on you pipe. Every motor breathes differently. Some have to rejet for the DG, some don't. What's you plug look like?

[longbedGTs]

I'll pull the plug in the morning but won't it be inaccurate since I haven't been able to run the motor with the choke off? I'm getting a better understanding of jetting(thanks to this thread and others) so I'll probably end up picking up an assortment and just experimenting until the plug shows a nice color. Thanks for the help!

[Gator72007]

Thanks for the write up! Last weekend i finally got time to mess with my 250sx's carb, its always had a dead bog if you cram the throttle so i spent a few hrs going through it and then adjusting the needle height and air screw, well it still boggs, but not near as bad as before. I got done that night and googled 250sx bog and came across this post and read all pages, in the end it looks like its inherent of the carb. If anyone finds the cure let me know

[Flyingw]

That problem has me stumped. Some carbs do, some don't but most have that problem to some degree. I have taken more than one carb with that problem and swapped every part out only to have the same problem so the problem is in the body somewhere. Most of the carbs still out there work ok if you don't stab the throttle. Once it gets past that flat spot, it works just fine.

[Gator72007]

Yea mine is fine to ride and ride aggressively, and not a real problem, but its always bothered me that i cant cram it to wot from low rpm's
I havent been on here in a good while, i read a few days ago about the 250sx/es 350cc big bore kit now available,
Thats something id like to do one day and then upgrade to a different carb

[longbedGTs]

Got it all buttoned up with a 45 slow jet and what do you know it runs with the choke off! Took it for a short ride around the house(didn't get out of 2nd gear) and it seems to run real smooth other than the slight bog that gator mentions above. I almost forgot the instant torque of the 350, it was great! Pulled the plug and it's pretty black which makes sense because I had to back the pilot out about 1 turn or so to get it to idle smoothly(had an intermittant "huff" with the pilot at 1 1/4 turns). It's probably about 2 to 2.5 turns now but idles really smoothly. I'll keep an eye on the plug color though as I don't want it to run too rich. Initially, I had the pilot jet oring in the incorrect place. Do you think that might have been partly the reason it wouldn't run with the choke off? Thanks again!

[captainweezy]

Such a great thread here Jim. Like your rear diff tutorial I have used these many times. this deserves to be a sticky.

[whiteman350x]

Ok i know this post was started forever ago but, in post #2 you said the qa04a the 85 trx250 carb will not let the es/sx run right but i never saw it explained why. I know I have an 85 trx carb in my pile and want to know why I should avoid it.

[atc007]

Nothing at all wrong with the 85, just drill for cold start if your weather gets much below 20D. Simple fix.

[Swany10]

Ok i know this post was started forever ago but, in post #2 you said the qa04a the 85 trx250 carb will not let the es/sx run right but i never saw it explained why. I know I have an 85 trx carb in my pile and want to know why I should avoid it.

I think the answer is in post #132 on page 9

QA04 or the QA09 (TRX250) don't have a primary jet

I'm looking for a replacement for my QA02 carb, ideally a QA07 or QA08. I saw an 86 TRX250 near me for sale for cheap and thought about getting it for just the carb, but I didn't know if the carb was compatible with my 86 250ES. That led me to this thread, and from what I can tell it wouldn't work for me.

While I think I found the answer, I don't really understand why it is though, the motors are the same, why don't the carbs swap?

[Flyingw]

Actually It will work. When I posted that comment, I was fighting with a couple of bad carbs. I have since rebuilt and run the TRX carbs on my test stand and they do run ok on an ES motor but the stock TRX jetting needs to be fattened up a couple of sizes on both the slow and main jets.

[Swany10]

Interesting. Does the 86 TRX carb have a screw in start up jet like an 86 ES does? I like the idea of getting my bike "back to factory" and finding a QA07 somewhere, but for practical reasons all I really need is good cold (MN cold) start performance. Would it make more sense to just drill out my QA02A?

[Flyingw]

You can drill out the 02. Yes the 86 TRX carb does come with a screw in jet. I drill all the startup jets on the carbs I rebuild for guys. All of them...

[Flyingw]

I can drill a couple of jets for you if you want to pay the postage. On the 85 carbs, get your hands on a #4 sheetmetal screw, Screw the screw in to the jet about 1 1/2 turns. I took an old flatblade screwdriver and cut a slot in to it. I put a piece of metal up against the jet tower, stick the slotted screwdriver up under the screw head and lever the jet out.

[Swany10]

You can drill out the 02. Yes the 86 TRX carb does come with a screw in jet. I drill all the startup jets on the carbs I rebuild for guys. All of them...

Well that settles it, I'll drill the one I have. If that goes badly for me somehow, I know where I can get a cheap 86 TRX carb to replace it with. Thanks for the insights.

[Flyingw]

Just be sure its a micro drill bit. I had guys who misunderstood the drill bit dimension and drilled a huge hole in their jet and ruined it. .80mm

[Swany10]

Something like this?
https://www.mcmaster.com/2951A47/

I can slip that in at the next order at work.