'86 250sx Cold Start Difficulties

[Xhumeka]

So I've been procrastinating from trying to fix my cold start problems on my '86 250sx because frankly - I'm scared to take apart a carb! I've never done it before, and it seems rather daunting to a newbie.

That being said, I'm willing to take my time, take lots of pictures, and follow my workshop manual to take it apart and clean all the jets and passages if necessary, but I wondered if there's ANYTHING else I should try before attempting a large (for me) project like taking apart my carb.

Some carb cleaner aeresol cans say you can spray the cleaner directly into the air intake of the carb with the engine running - should I try that before I remove everything, or is that a bad idea?

The engine seems to run GREAT once warmed up... no bogging or missing. Once warm, it also starts up like a champ.

The only problem I have is cold starts... no amount of choke seems to help. In fact, I've never been able to start it with any amount of choke - I have to crank the engine over for quite awhile (no choke, applying throttle every now and then) before it finally starts to catch.

Once it finally starts, I have to give it about a 1/8 throttle for 10-15 seconds before it will idle on it's own. If I apply choke at this point, the engine dies - so that seems to imply to me that my choke/starter valve is working.

So once it starts, everything is great... it's just GETTING it to start is the challenge!

Any help greatly appreciated!!

[honda200x1987]

When there is a problem with cold starting it could be as simple as replacing the spark plug, use NGK OEM spark plugs. The other problem could be your carb. First clean your air cleaner box and change or clean the air filter. The carb may need a little cleaning. One other problem could be your engine is burning oil making it harder to start when cold...Does it smoke?

[userj8670]

Hey man carbs are cake. Take it off the bike which im sure you can figure out how to do that. Then there are 4 screws that hold on the float bowl. You take that off and there are 2 floats and a piece that they lock into (all plastic). Take them off (easlily just lift up and slide the pin out for the floats) and there are the jets. Take those out and blow them out lots of carb cleaner. Make sure the inside of the carb is spotlesss!

[Xhumeka]

Sorry, I should have mentioned that I already replaced the spark plug (brand new, properly gapped) as well as ensured the airbox and air filter are clean as a whistle.

The engine is not burning oil (at least it doesn't smoke).

[honda200x1987]

Sorry, I should have mentioned that I already replaced the spark plug (brand new, properly gapped) as well as ensured the airbox and air filter are clean as a whistle.

The engine is not burning oil (at least it doesn't smoke). Then you need to clean your entire carb, that should be the problem.

[thestud25]

Your intake valve may be tight as well.

[oldskool83]

Check both valve clearances, hard starting is a sign intakes are tight. mx xr200 has a .0000 gap, started after like 30 kicks...ajust them and started 2nd kick.

[Xhumeka]

Ok, thanks... I'll check my valves first then. A buddy of mine has a dr350 dirtbike, and when his valves went out of spec it was actually harder to start HOT than cold, so I didn't even think about that...

[Silverado]

Xhumeka, let me know how the carb clean goes....I need to do the same on my 250sx but again, it does seem rather daunting !

[Xhumeka]

Xhumeka, let me know how the carb clean goes....I need to do the same on my 250sx but again, it does seem rather daunting !

hahah, will do!

I just find it odd that the only problem I have is starting it... once it's started, it works GREAT! I always thought a dirty carb would cause more problems than just being hard to start.

[Thorpe]

The carbs on those machines, (and the BR 250es) are prone to start like crap in the cool weather... There was a fix from honda with a larger pilot jet... Read this post

http://www.3wheelerworld.com/showthread.php?106592-Cold-Starting-quot-85-250ES&highlight=250es+coldstart

[Xhumeka]

The carbs on those machines, (and the BR 250es) are prone to start like crap in the cool weather... There was a fix from honda with a larger pilot jet... Read this post

http://www.3wheelerworld.com/showthread.php?106592-Cold-Starting-quot-85-250ES&highlight=250es+coldstart

Ok, thanks... I'll check that out, but I thought the cold start kit was only for 1985's (and that 1986 models had the "problem" corrected).

[tundrawolf]

Friend, carbs are so easy. Once you do one, you have done 80% of the cars out there, most cars included.

The first step is to work comfortably on a smooth, flat surface, with PLENTY of places to put parts. You don't want just one cup or bowl, because if you are new to it, you are going to want to put things in cups according to sequence. However, a good exploded diagram will actually save you a lot of headache, but it is still good to take things apart in sequence.

It will help you to also put things in each bowl in segments, too. For example, the mixture screw assembly has the screw, a washer, and a spring. Put all 3 into a separate container. The slide has a clip, a circlip, the slide, and a needle. (more or less depending on carb)

Write down your jet sizes, it will help us help you figure out your jetting. The sizes are stamped onto the sides, or the top, sometimes the bottom, of the jets. Hard to see and may require some polishing to see.

Be wary of springs that may want to escape after being trapped inside a carb for years at a time. And who can blame them?

Try not to bend *anything*. Your float level can be messed up easily-but have no fear- at Autozone, there is a slide gauge you can buy for less than 200 pennies. I have one, it is invaluable for float level adjustment!

When you clean it out, do yourself a huge favor and break out your dremel. After every part has been removed (In other words, the carb is a shell, and all one color-gray) fit your dremel with the wire brush and use a low RPM to polish the bowl, and inner area where the jets screw into. You don't have to make it shine, but you do want it all to be a light gray color. Get all the rust, crud, etc out.

Next, using carb cleaner, or, what I personally prefer-brake cleaner and the straw (Carb cleaner without a straw is as effective at cleaning out ports as a garden hose) get your safety glasses on, and stick the straw into, or on, every port. Make sure the spray comes out *somewhere*. If it squirts back at you, that might not mean it is clogged, only the passage is small. If you find a clogged passage, be very careful when you clean it out, especially if you use a sewing needle. Because you can enlarge the port (This applied to the jets, too) and throw off your mixture a tiny bit. So just be gentle. It's no big deal. When I was a kid and I did my first carb I absolutely had to enlarge every port. I went to town on that carb. The engine ran, but had black smoke after that.

If you want, use a small flashlight to shine in the different ports and see if you can see light in other ports. This will help you understand where the gas is going, and where the air is going, too.

Use the de-fluffed end of a Q-tip and some brake cleaner in the needle valve seat. Push it hard and turn. This will help remove the garbage around the seat, in a carburetor that uses a fixed seat. Most carbs use removable seats-if that is the case just put the new seat in.

Use a good engine degreaser to hit the outside of the carb, and a wire brush and some Q-tips.

You are running the risk of breaking the gasket(s) and having downtime if you try this without a rebuild kit.

Be careful with the float, it's fragile, but not delicate.

Pa attention to how the needle valve goes back in. The pointy side goes into the carb, the springy side goes into the float. This error is one of the things that caused me to buy my ATC110 for $35. No big deal.

Don't strip any screws. The bowl screws may be in there. Take your time and get the right screwdriver. Push DOWN as hard as you are turning. Sometimes more so. Or, other times, they are loose.

Take your time, take your time, and don't be worried. When I was a kid a neighbor offered to help me fix my motorcycle. He took the carb apart as I watched in horror. Finally I said "Are you SURE you can put it back together again??" seeing all the pieces. I thought there was no way. But, he had it back together perfectly. Carbs are super simple, even the "complicated" ones. The two worst things you can possibly do, are 1. Be afraid and not do it at all, and 2. Go fast and end up tweaking something and forgetting how it goes back together.

This is a lot of info but you will be fine.

You can always post a picture here and we will tell you how to get it back together.

[Xhumeka]

Be wary of springs that may want to escape after being trapped inside a carb for years at a time. And who can blame them?

That line practically made me spit my coffee out from laughing!! Thanks for the chuckle!

And an even BIGGER thanks for taking the time to type all that out... LOTS of great info there, and I'll definitely take your advice. I'm going to clean it out, write down the jet numbers etc, and if I'm still having problems afterwards I'll post the numbers to see if there's something else I can try.

Thanks again (to everyone) - I'm going to try to clean it out this weekend and will report back after doing so.

[ailll1]

i heard that only 85 250sx and es carbs had cold start problems also
actually mines needs to start with choke but wont run if its on when the engine is cold
got to put it off as soon as it starts(keeping it running with throttle for first secs)
hopefully mine doesnt need so many kicks to start(3-5 max)

[Dirtcrasher]

I have a topic called "carb 101" or something here from years back, decent read and info...

Your 86 carb should say "08" in the part number on the KEIHIN carb or it is not the updated carb that starts/runs great in all weather.

Take all the jets out, clean it and adjust the valves; The problem should disappear................

[Xhumeka]

Well I pulled the carb apart today, trying to follow both the honda manual linked in these forums as well as a clymers manual.

Got it MOSTLY apart I think, but have a look at the attched picture... I'm assuming that #24 piece has to come out, but I don't want to force it so I just wanted to be sure. Also, can you see any other parts that need to come out before I start going to town with the carb cleaner? I followed the manuals as best I could, but some instructions were a little vague...

[Dirtcrasher]

I'm not sure what part you need.... Maybe Sudcco sells that brass insert for the float valve but I can't see a rubber tip wearing it out. I have never replaced that pice and it is NOT in a rebuild kit. But, you didn't remove the side mounted starter or sometimes it's called the pilot let. On the top of that tube there HAS to be a rubber plug or it won't work. Many an SX I bough was missing that rubber plug and seeing that it sits in gas, you must have it!

I can see your side (starter jet) which means it's a Keihin 08 written on the side just above where the fuel bowl mounts.

I like the guy that recently talked about soaking his carb and running air through it, then watching the bubbles. I think he finally used a bucket of that "carb soak" and then had more bubbles so whatever he did, he cleared it :beer (Wish I could find that post!)

Lastly, after the main jet tube comes out (now the whole thing is like a 1 and 1/2"s long) and under that is what most people call the "needle jet" ic can go in either way but the side that shows how it fits in the cupped end of the "needle/main jet holder" does come out very easy. You have to use a small punch and tap it down from the top. It has a HUGE hole so if it's clear, don't even touch it.............

Just get every other jet and passage clean and your chicken! You have the "GOOD" cold start carb :D :beer:

DC

[Xhumeka]

ok, thanks dirtcrasher.

i have the rubber plug, I removed it before taking the picture.

in my honda service manual, it says in bold letters "do not try to remove the starter fuel jet from the carburetor body".

is it safe to remove it to clean? why would the honda manual tell me not to remove it, any idea?

[tundrawolf]

It may be a press fit into the carburetor. If that is so, then you would need special equipment to remove it, and probably damage it in the process. It may require something being threaded into it to be removed, ruining the jet. You should be able to clean it, or at the very worst, let it sit in carb dip overnight. It looks like your needle seat (The gold circle) may also either be a press fit or an interference fit. Does the diagram you have show the needle seat with an oring? If so, then it is removable. Take a look at the rebuild kits on ebay and see if they come with the needle seat, if so, then it is definitely removable.

[Dirtcrasher]

ok, thanks dirtcrasher.

i have the rubber plug, I removed it before taking the picture.

in my honda service manual, it says in bold letters "do not try to remove the starter fuel jet from the carburetor body".

is it safe to remove it to clean? why would the honda manual tell me not to remove it, any idea?

That "side jet" comes right out, it is externally threaded just like any other jet and or bolt.

Honda may have said that because the 85 jet was pressed in and not the easiest thing for a novice to remove.................

[tri again]

underneath one of the screw out jets , there is another brass tube like an inch long that just sits in there.

check the 3rd hole from the left or the 4th from the right/float seat. sure looks like it might still be in there

I missed it on my first 86 carb redo but was able to pluck it out with a non round toothpick and it really was rusty mucky. some kind of emulsifier tube? prob why i think I can see it in your picture.
(flashbacks)

my uncle used to check jets by throwing the whole carbs in a bucket of hot water and mouth blowing thru them with a piece of fuel line.
Clean see thru jets mean nothing if the passages are plugged, right?

He''d either put in lemon juice or vinegar in the water sometimes but that may have just been part of his mysterious sense of humor. or a reason to send me out of the shop for a while.
Lemon juice was prob for his tea.

yupp, screamin hot water works better than anything for that built up sticky sludge accumulations of old cleaners and lubes.

[Xhumeka]

Thanks guys!

After cleaning everything I put it back together and it starts MUCH better now. I let it idle and warm up for 5 mins, and it idles nicely and isn't missing or stuttering during idle.

The one remaining issue is when I blip the throttle from idle, it Bogs and will die if I don't release the throttle right away. This only happens when I go from idle to WOT VERY fast, again blipping the throttle. I can increase idle fairly rapidly without stalling - it's only if I blip it as fast as I can that it bogs out.

My pilot setting before cleaning the carb was 2.25 turns from fully seated, and when I re-installed the pilot screw I left it at this setting. According to my manual, factory setting is only 1.25 turns from fully seated... should I change my setting to factory setting and see if that improves throttle response, or should I be making an adjustment somewhere else?

Thanks again for everyone's help... it's definitely much better than before after the cleaning!! (at least in terms of cold starting!)

[tundrawolf]

It is good to hear that you were successful! Does it still bog under the same conditions while you are riding it? I had an 05 450X that had a bad bog from idle while in neutral-but that was actually normal. In gear it ripped, no bog.

[Xhumeka]

It is good to hear that you were successful! Does it still bog under the same conditions while you are riding it? I had an 05 450X that had a bad bog from idle while in neutral-but that was actually normal. In gear it ripped, no bog.

That's a good question... the problem is that I live in the middle of a big city (approx 6 million people) so I won't have the chance to take it for a run until this weekend at the earliest (unless I want to risk running it up and down the street, but that's just asking for trouble).

Maybe I'll try adjusting the pilot screw as per the manual to start with, and then just wait till I can take it for a good test run before adjusting anything further.

Once again a big thank-you to everyone's help!

[tundrawolf]

We are happy to help. The bog on the 450X was a common problem. On thumpertalk.com there were many complaints, and it only happened when the engine was under no load. People tried, but were unable (Short of the purchase of the accelerator pump upgraded cover) to cure it. I personally was upset, a brand new bike, that bogged like some $100 garage sale find. However it seemed to run fine, better than fine, and it turns out that was just the way it was. It's too bad you are in the city, I hope you can get it out to test it soon.

[Dirtcrasher]

They say that once your past the proper amount of turns "out" on the air screw, to change the pilot jet up one size. Then that screw should get back down to 1.5 turns out or whatever it's suppose to be. The screws themselves do wear out because people over-tighten them..... If the screw is out too far, it can fall out (it's happened to me....) then your screwed :D

You should be AOK but I've bought a couple of carb rebuild kits that have the wrong pitched thread on the air screw. I can't imagine how many guys have forced them in there and ruined the whole carb and or the screw............ Pisses me off to buy an 18$ kit and shipping only to have that screw NOT fit; And most of the time, I'm buying the kit specifically for that air screw!!

[Dirtcrasher]

I am looking for a top of the line exhaust manufacturer. Pro Curcuit e mailed me that they do not manufacture a exhaust for a 86' ATC 250R. I would like a loud tailpipe cause I'm from the oldschool believing loud tailpipes save lives. Anyone with any suggestions? Thanks.

PLEASE, think about it for a moment. EVERY post within here relates to "cold starting difficulties", do you think the 250R guys are gonna read this?? I read ALLOT of topics but only if the catch my eye or it's something I own.

PLEASE, start a new thread and plenty of R owners will see it and try to help :beer

[tundrawolf]

I can't imagine how many guys have forced them in there and ruined the whole carb and or the screw............ Pisses me off to buy an 18$ kit and shipping only to have that screw NOT fit; And most of the time, I'm buying the kit specifically for that air screw!!

The previous owner of my V Star 1100 had turned the pilot mixture screw in so far that the needle had seated to the point where when it was backed off, the tip of the needle broke off inside the seat. So, he just opened up the butterfly to compensate and created an extremely unbalanced engine.

[Xhumeka]

Update!

A big thanks to tundrawolf who has sent me a few PMs recently trying to sort out my bogging issue. On his recommendation, I was going to try dropping the needle clip a notch. Before I got that far, I discovered something...

When I first removed the pilot screw to clean the carb I thought I removed every part... but have a look at the below diagram:

http://www.ragefaction.info/images/psych0/orv/1986_Honda_250SX_ATC/250sx_carb_pilot_screw_orings.jpg

My pilot screw had an o-ring near the screw (o-ring #1 in the diagram) so I thought that's what the exploded diagram was showing. But it appears there were actually TWO o-rings, and one is seated at the very bottom of the pilot hole (o-ring #2 in the diagram).

Now knowing that there should be another o-ring that comes out, I had a closer look with a magnifying glass and a flashlight, and I finally found a BADLY DECOMPOSING o-ring... it barely was holding together at all and little pieces of rubber the size of sand were coming off of it. It definitely was not creating a proper seal.

So I have a feeling that little culprit is what is causing me grief (hopefully!). No doubt those little rubber particles have worked there way into passages and must be forced out with a lot of compressed air. I don't think carb cleaner will help much, as it would take a long time to break down rubber.

So it looks like I'll have to order a carb rebuild kit unless I can find that tiny o-ring somewhere local.

But with my limited knowledge of carbs, it seems reasonable to me that rubber particles are blocking (or at least restricting) passages making cold starting difficult and that a badly decomposing o-ring on my pilot screw is letting air in which might contribute to my bogging? Does that sound like a reasonable explaination to you guys?

[tundrawolf]

I think that definitely could be a factor! Now is the time for compressed air. Blow out every port and passage, it should clear out any decomposed Oring particles. I wonder if carb dip would have an effect on the decomposed Oring matter?

I also am wondering now what the difference is between the updated carb and the original..

[TeamGeek6]

"The only problem I have is cold starts... no amount of choke seems to help."

Thats probably not carb, its probably IGNITION. Remove the spark plug, if the insulator is brown/black then its fouled. Look at the insulator under a strong magnifying glass,
tracks might be visible wher the spark is arcing down the side of the insulator.

My R was a nightmare to start till I rebuilt all the ignition wiring, now it starts on a half kick when its anywhere near warm outside. There was a loose connection
on the CDI plug which caused the ignition to cut out. The spark was dull orange instead of blue/white.

[Xhumeka]

Thanks TeamGeek6, but I have already replaced the spark plug with a properly gapped NGK DR8ES-L plug (as per the service manual) and it didn't help one bit :(

[Woodsrider]

Thanks TeamGeek6, but I have already replaced the spark plug with a properly gapped NGK DR8ES-L plug (as per the service manual) and it didn't help one bit :(

I think he was suggesting that you remove the plug so that you can inspect it for signs of a weak ignition system....not to change the plug.

[Xhumeka]

Ok, so a bit of an update on my cold start difficulties...

After I originally cleaned the carb, it seemed to start better the first time, but each cold start after that it became harder and harder and within a week it was back to the original problem - having to crank it for 10 second bursts at least 5 times before it would finally catch.

So I decided to order a "Shindy Carb Rebuild Kit" from eBay ($21 from seller ghdiscountatv).

Last night I tore the carb apart again, this time replacing everything that came in the kit. I also wasn't as 'gentle' with the compressed air - I shot some carb cleaner into an opening, then squeezed the rubber tip of the air compressor hose into each opening I could find, and blasted it with 10 seconds of compressed air.

I put it all back together (let me tell you, nothing is more frustrating than trying to squeeze the carb on a 250sx back into position with my big hards) and crossed my fingers as I gave full choke and hit the start button.

crank, crank, crank, FIRE! Started to purr like a kitten! Slowly turned off choke and it behaved PERFECTLY.

This morning I woke up hoping it wasn't all just a dream, and it started up FIRST crank with full choke... man that's such a sweet sound!

So I think I finally got the carb issues sorted out! Thanks again to everyone's help and advice - you guys rock!!