Strange carburetor question

[tundrawolf]

I have a Honda ATC110.

It has a Keihin carburetor. It ran pretty good when I got it going a week or so ago. Here are the symptoms of what it is doing:

1. When it is cold the idle is very high. As it warms up, the idle drops down very low.

2. I noticed black smoke out of the exhaust while it is idling, but if I go to a smaller pilot jet the engine bogs so badly it stalls when I give it gas. I tried leaning out the needle, and all that does is completely kill my top end power.

3. It seems to have a bog after 1/3 throttle sometimes when cold ish.

I notice black smoke all the time but if I lean anything out the engine bogs like crazy.

Any ideas?

[shortline10]

Make sure all the air intake boots are sealed up good a 110 motor needs a good amount of intake back pressure to run correctly and a good way to tell is while your riding it just to the point were it likes to bog down reach down and chock it alittle to see if it clears up , what this is doing is creating back pressure manually .



I have a Honda ATC110.

It has a Keihin carburetor. It ran pretty good when I got it going a week or so ago. Here are the symptoms of what it is doing:

1. When it is cold the idle is very high. As it warms up, the idle drops down very low.

2. I noticed black smoke out of the exhaust while it is idling, but if I go to a smaller pilot jet the engine bogs so badly it stalls when I give it gas. I tried leaning out the needle, and all that does is completely kill my top end power.

3. It seems to have a bog after 1/3 throttle sometimes when cold ish.

I notice black smoke all the time but if I lean anything out the engine bogs like crazy.

Any ideas?

[tundrawolf]

I have gone through the carburetor and the intake and it is pretty airtight. Something is very odd. It smokes a bit of black smoke, but bogs like crazy when cold, runs very cool, fowls plugs, but when I go leaner on the needle, it barely even runs at all.

The odd thing is that it will idle very quickly when cold, then nearly die if I do not keep on the gas when it is warm. If I adjust the screw to keep the motor running when it is hot, when it is cold the engine will be racing.

[200XMichigan]

I would really try real sealing the air intake tube. I had a Trail 90 that did the same thing. (Pretty much the same engine) I put the air intake tube up against a straight edge and it wasn't perfectly flush. I just placed some sand paper on the work bench and sanded it so it was a flush surface and then sealed it up with some sealant. Runs great now.

[tundrawolf]

Alright, now you guys have my attention. I will seal it up today and report back.

What do you guys think, should I use the cylinder head to intake gasket and silicone both sides, or should I do away with it and just use silicone alone?

[Mr_RPM]

reach down and chock it alittle to see if it clears up , what this is doing is creating back pressure manually .

thats my favorite part for a true choke and not a fuel enrichener, good for diagnosing. one thing ill miss from my old carb!

[200XMichigan]

For a lot of parts that come in contact with gas I have used Permatex #2 Flexible gasket maker, I would cut a new gasket and use the sealant. Make sure to wait until it has set up to try to fire the engine otherwise the gas will thin it out.

[tundrawolf]

So I took the carburetor off and found what looks like rodent droppings and urine in the bowl. But the carburetor and throttle valve were always installed. I used some sandpaper on a flat surface and found that the edges of the intake manifold were facing downward, not creating a good seal. So I searched for an hour for my gasket material and did not find it. So I took a corn flakes box and made some gaskets.

http://img.photobucket.com/albums/v237/wolfmangk/ATC/IMG00001-20101113-1412.jpg

I used brake cleaner to clean them up, it got all the ink off of them. Then, I applied gasket maker to each sealing surface, around 7 of them! I allowed it to tack p before I assembled it, and let it dry some more.

I also put some teflon tape on the idle adjustment:

http://img.photobucket.com/albums/v237/wolfmangk/ATC/IMG00002-20101113-1440.jpg

I cleaned out the bowl and jets and ports and passages. Now, it still smokes black smoke but the bog is gone. It is running fat now. The idle is still really high when cold and lowers when warm. It also seems to act like the throttle cable is catching, but I lubricated it recently and it is definitely not sticking. I think it may be a fuel or jetting issue that seems to hang the idle.

[beets442]

Make sure the end of the throttle cable is seated correctly in the throttle slide...Beets

[JGedmin]

Make sure the end of the throttle cable is seated correctly in the throttle slide...Beets

definitely check that the slide is returning all the way down. cable on my 185S was backed out of the plastic cap keeping it from idling low and was smoking like crazy until I adjusted it by screwing it in all the way. sounds like yours might be backed out a bit.

[tundrawolf]

Can anyone tell me what the stock jetting size (Main and pilot jets) were on this ATC? I was told it was an 1983 I think... It belches out black smoke which isn;t good but it has never run better. I think the idle not going down is due to the massive pilot jet I needed to keep it from bogging down.

[MonroeMike]

Run your VIN - http://atcvin.webs.com/

Carb Specs.

http://www.3wheelerworld.com/attachment.php?attachmentid=83703&d=1258781850

[tundrawolf]

OK so I put the original jets back in. There is no black smoke now, but the bog is back. I tried richening the needle, but it doesn't help. The pilot jet I took out of it is around size "200". The hole was huge. That is probably why I get all the black smoke. The main jet was normal size. If I rev the engine quickly the engine will bog and stall. When I rev it quickly and hit the choke it will pick back up and run fine. SO my options are a rich engine that runs good and fouls plugs and belches black smoke or an engine that runs so lean it bogs out and stalls when you give it gas too quickly?

[Jeepermc]

When you hit the choke and it clears up you are taking away air from the mixture and richening it..Not leaning it out.......It sounds like you need a bigger main jet...If it idles nice leave the pilot jet you have in it... Start off with the needle in the middle setting. Play from there.

I am by no means a jetting expert so if I am wrong on any of the above counts please correct me.

[tundrawolf]

I understand that about the choke richening the mixture up. The choke had no effect/detrimental effect before, now it seems to have a positive effect depending on RPM and load. Before, when I gassed it quickly, the engine revved well and belched black smoke. The engine smoked black at idle, and when revved also put out black smoke. Now, no black smoke, but an extreme bog that will kill the motor if I keep the throttle held open. I did not change the main jet. The needle position helps, but does not eliminate the problem.

Perhaps the ultra-large pilot jet compensated for a small main jet?

It is definitely down on power right now.

[tundrawolf]

Hello guys, I need help. At 1/4 throttle it drives fine when cold, but any more and it bogs way down unless I let up on the throttle. It lacks major top end power.

I have the carb apart right now and a tool I can use to ream the jets out a little at a time. Does this sound like a main jet that needs to go bigger?

[tundrawolf]

Ok so I put the original jets back in. Also the needle collar in the carb. Now the bog is so bad at full throttle the engine bogs and dies. It only runs now at partial throttle.

If I hold the choke halfway it runs perfectly.

Could it be that the choke reduces the velocity over jets that are too large so it runs properly? Or am I way off base here.

The carb kit came with jets that screwed into the carb ok but were slightly different in shape. It came with a white float with an adjustable tang which I set at stock height. I am at a loss here guys.

[ezmoney1979]

I have also struggled with an issue like this on a 110. As mentioned earlier they really need the correct amount of intake back pressure. Make sure your ENTIRE intake system is in check. This includes air filter, boots ect. I remember mine would run horribly with the just the air filter removed. Good luck!

[tundrawolf]

That's just the thing. I have checked everything. I recently cleaned the air filter but it is a paper unit and I can only make it so clean you know? I'll blow it out tomorrow. I used oil on the outer filter cover to trap more dirt could that be hurting me?

[200XMichigan]

Did you make sure you don't have an air leak? If the bogging stops when you choke it I think you have an air leak. That's exactly what my Trail 90 did until I found the air leak. Pretty much the same engines as far as most things are concerned.

[tundrawolf]

I sanded the flanges on the intake on a flat surface, made some gaskets, and put silicone on both sides of everything, even the oring. Everything from the cylinder head to the carb should be ok.

Whenever I take the intake off though the bolts are looser than a left them but, still tight.

[200XMichigan]

On the carb side? Mine did this too. They were soft but not stripped. I put a stud in and a nut on the back side of the stud on the intake and used nuts to then hold the carb on. Took care of the problem. Doesn't loosen up anymore. That's your air leak I bet.

[tundrawolf]

Did you drill and tap the threads for one size larger?

[tundrawolf]

So what should I do? Run a tap down the hole and then run a stud all the way down with maybe some red loctite? What thread pitch and length stud do I need. Does anyone know? Happy thanksgiving!

[tundrawolf]

I went to my local cycle supply to get the right jets (35 slow, 85 main, it has a 38 slow and a 72 main in it right now).

The guy could not find the right jets, so he had to order them from Honda, and the total was almost $24! I need it to run right, because I am finding many uses for it instead of beating my V Star on the dirt roads around here.

Also, I bought some 3" fully threaded bolts (6x1 metric of course) to use as studs to hold the carburetor to the cylinder, because the bolts were always coming loose.

I removed the studs from the carburetor flange and used the stock bolts from the cylinder and some locknuts to hold the carb to the intake, after I reamed out the threads.

So I have already run a tap and cleaned out the threads in the cylinder, as well as sprayed brake cleaner down the holes then blew them out with compressed air. Next I will clean the threads of the bolts with a brush and brake cleaner and put blue loctite on them and thread them down until they stop.

I am hoping this will cure any vacuum leaks I have in the intake system. I also decided against using locknuts on the intake to cylinder connection because I do now want to put undue reverse tension on the studs.

So you can see why I spent so much money on the jetting, I do not want to be doing this all over again any time soon!


Edit: I am kind of torn. Should I keep the heads on the bolts so I can tighten them good, and cut them off when the loctite has cured, or cut the heads off, and double-nut it to get it tight? Anyone?

[tundrawolf]

OK So I borrowed some Loc-Tite from a friend, and it turned out to be penetrating green loctite. I hand tightened the studs with the loctite, and dry fitted the intake to the cylinder. I got the jets today, and put the intake back on, and I am waiting for a 24 hour cure for the silicone so I will start the bike tomorrow. I put a fuel filter on both the reserve and main lines because I don't want to have to fuss with the carb again because of any clogging or debris issues.

I can't wait to fire it up with the right jets in the carb for once, and no intake leaks! If the studs do not fix it, my friend has a 6x1 heli coil kit and I might try to fix it with that.

I will get pics up of the clearancing I had to do to fit the intake.

[tundrawolf]

Ok so I was way too busy today to even start it. I guess the silicone will cure for 48 hours.

[Pafrig]

maybe its not the carb! dont you have another 110 that runs? (the one with the funky tire?). i would check the ignition timing. or check the point's gap.

[tundrawolf]

You could be right. I have been able to hook up the pulse generator to a tachometer, but the reading is way too low to be usable.

If I have 400 rpm at the 4 cyl scale, for the 1 cyl reading would it be 1,600 rpm? That'd make sense if it was.

[Pafrig]

i would just set it extremley retarted and see how it ran, then set it extremley advanced and see how it ran. then sorta figure out where it likes to be. I found that it likes it right about dead center. you will notice that on that little golden colered plate that the exciter coil is attached to has a little notch in it, and that notch has some play around a little part in the aluminum casting that it bolts to. this is the adjustment parameters. also, set the pilot screw to 1 turn out from seat.... have you checked that your float level is correct?

[tundrawolf]

I finally got time yesterday to start it and run it a little. I had to adjust the idle screw in a lot just to get it to idle, but it idled pretty good. I go walk down to do a chore and when I came back the idle was way high. So I quickly shut it off and messed with it some more.

The bog is completely gone now, which was my biggest concern. But now I cannot get the idle to stay the same. It will be idling fine, then just taper off until the engine stalls. Or I will give it gas on the trail and it will hang idling a little high.

It is not the cable or the slide, I have lubricated the cable thoroughly many times, and even adjusted 3/4" of play in it.

Today I started it and it started up fine and idled fine, (Without me touching the throttle) then just suddenly tapered off and died with what sounded like a muffled backfire through the air filter. It did this several times.

I have checked the float level recently, and I have not messed with the ignition.

Does anyone have any ideas? I can't leave the engine running because it will surge or die or both.

Oh, and like it has always done, the air screw has zero effect on the engine rpm.

[tundrawolf]

I timed it at where I think 1,700 RPM is (My automotive tachometer shows 350 RPM on the 8 Cyl when the engine has to be at 2,000 rpm or so, but who knows??) and I even tried changing out the air screw and slide and needle and the RPM still races, or drops so low it stalls without me touching it. The air screw, when it is all the way in and seated seems to increase the idle when the idle is surging. As I turn it out it seems to drop a few RPM but is still surging.

[tundrawolf]

My idle problem is very frustrating, you know? Just for kicks I disconnected the throttle cable from the slide and put the slide in and the spring, and screwed the cap on. I started it, and with a little application of the idle screw, when it was at about a "normal" idle, it suddenly began flying out of control and I killed it.

I have tried:

A new jet kit
The stock jets
Securing the intake and carb with studs and nuts and bolts
A new float
A new needle valve
Cleaning every crevice, including drilling out the brass ball and making sure the passage was totally clear
Different air screws, including aftermarket, an aircsrews from different carbs on CT110s
Different slides
Different needles
Cleaning the air cleaner
Soaking the carb in carb cleaner overnight
Blowing/spraying out every passage with air and carb cleaner and brake cleaner
Changing the brass needle valve, but went back to stock
Completely disassembling the ignition advance mechanism, cleaning, polishing, and lubricating it
Making sure the cam is in time with the crank
Adjusting the valves (But a while ago)
Tightening the cam chain
Adjusting timing to the F mark
Replacing the spark plug

It used to have a terrible bog that would happen if I gassed it too quick. Now the bog comes back, but only when it is cold and at close to full throttle, if I do not let off when the engine is loaded, the engine will bog and stall.

And the idle fluctuates from barely running to screaming full throttle with one or two turns of the idle screw, and will go from one extreme to another over the span of a few seconds, or a minute, and never stays the same. This problem has been with me since I bought the bike. (It is not the throttle cable, see above-I disconnected it and it still does it)

It used to constantly but slowly drip gas from the carb, but the new adjustable float allowed me to put a stop to that.

My only option is to set the idle so low that it will instantly die (But will not surge) and try to keep the gas on while I ride it, because if it surges in gear it can be dangerous on a tight trail.

The machine is so much better to get around with than my V Star 1100, not that the Star is bad, it does great in the dirt, it's just not made for it and it is my only transportation. So I really need to get this awesome little trike running right. The only thing I haven't done is changed out the carburetor. I am under and extreme budget so that is not really an option right now.

Please help

[MTS]

Sounds to me like a Valve train problem at this point...You have pretty much covered everything else...Not sure what you mean By setting the timing on the F mark...Thats for the ignition...For static timing set on the T mark if i remember right....a Bad intake spring/valve will Play tricks like this..as will a Broken spring in the Cam chain adjuster...

[tundrawolf]

Oh man I don't want to hear that. There really isn't any timing chain noise since I adjusted it. I also timed it with a timing light to the F mark.

Last night I sealed off the throttle cable cap with silicone thinking maybe it was sucking air in from there. This morning it had no effect, the idle still goes all over the place.

[Pafrig]

maybe the timing jumped a link??? im just confused now! are you sure that you have the CORRECT peices

[Pafrig]

oh, i dont mean to belittle you, but when you put the slide into the carb, you oriented it so that the little the little tapered indent is facing towards the side where the petcock and adjusting screws are, correct?? if it's in backwards, it wont drop down far enough. i thought this because if it revvs wilidly, there MUST be too much fuel air getting to the engine... and if the venturi is completley closed, that wont happen.

[tundrawolf]

Yes I align it every time, and I have tried different slides.

I have checked the timing notches and everything is aligned perfectly.

I took the air screw out when it was running and it surged way high. That is why I sealed the throttle cable (and I did a good job of it) because that is the only other place air can get in.

The only thing I am thinking is maybe the fuel is traveling some where into the throat, but no fuel comes out of the overflow.

[tundrawolf]

OK so I have been doing experimenting with float levels. I put it from 10.7MM to 11.3MM and finally 12.1MM. It still does everything it did before. At middle needle height at 12.1MM though it runs pretty good. If I set the idle to a normal RPM it will surge and rev to the moon eventually. If I set it lower it will idle OK for a second or two, then steadily drop in RPM over 5-10 seconds and just die.

I adjusted the valves, and verified valve timing and it actually idled steadily for a while, until I revved it, then it was back to square one.

Tried the flammable stuff around intake trick and it didn't surge idling.