1980 ATC 110 sputters and pops at full throttle

[derrick81787]

Hello everyone,

This is my first post here on 3WW, but I've read several posts and love that this place exists. Anyway, I'm brand new to ATVs, and I've started out with a 1980 Honda ATC 110.

I had a guy rebuild the top end and replace the carb right around Christmas time. When I got it back from him, it ran like a top and everything was great. Then just recently, I started having no power whatsoever at full throttle, and it sputters and pops (backfires I think) until it either dies or else I let off the throttle. The problem is worse in 2nd gear and higher than it is in 1st, but it exist no matter what gear it is in. My spark plug was black, so I thought that maybe it was running rich, but it's weird that the problem is just now happening and didn't happen back when I first got it.

The new carbuerator is a Chinese knockoff of an ATC 110/ATC 125 carb and looks practically identical to the original in every way. However, I'm not sure if the needle and the main jet are exactly the same or not. The problem is that while I'm pretty sure that I still have the original jet, I'm not sure if I have the original needle or which of my two needles is the original.

Of the two main jets that I posses, I have one that says "82" on it and that I believe is the original, and I have another that looks pretty much the same to the naked eye but has "876" on it. The one with "876" on it is in the carb and has been ever since I picked it up.

However, I'm not sure which needle is original as the guy who worked on it reused the top cap from the old carb, and I'm not sure if he also reused the slide and needle or not. While the guy was a decent mechanic, he was extremely unorganized, forgetful, and kind of unreliable (I don't plan on going back), so I don't think there's any point in me asking him because he won't know. Anyway, the needles are actually quite different from each other, so I'm wondering if that's the problem. One needle is brass, thicker, has a more aggressive taper, and has "336536" on it. The other is a silver color, thinner, has less of a taper, and I'm not sure if it has anything stamped on it as this needle is currently the one in use.

So I guess I have a multi part question: 1) Does it sound like my problem really is that it's running rich at full throttle or is it something else, 2) If it is running rich, am I on the right track with the jets and the needle (I have no idea what I"m doing but have managed to take it apart and put it back together and get it running again), 3) which needle is original and/or the better needle to use, 4) does it make any sense that it ran fine all of January and February but is now giving me trouble?

The symptoms made me think that I need a smaller jet, but one thing is giving me pause. My manual says that the original jet is an 85. However, from what I've read online that was changed to an 82, so that explains why I have the 82. The problem is that the 876 is either the same as the 82 or maybe slightly smaller, but it definitely isn't bigger. That makes me think that I shouldn't need an even smaller jet because I am already at least one size smaller than what is in the manual.

One last thing. I removed the thinner, silver needle and adjusted the clip by one position so that the needle sits lower in the carb. Then I started it up and drove it around. At first, I experienced all the same symptoms and thought that the adjustment did nothing. However, after driving it for a few minutes, it suddenly started working fine. What do you make of that?

Sorry for the long list of questions. I'm new to this whole thing, but I do appreciate any help that you might give.

Thanks,
derrick81787

[yaegerb]

So he rebuilt it, ran great when you first got it and now it is popping? Odd, almost sounds electrical unless you are using old gas and it clogged the jets while sitting or you could be getting junk from your fuel tank into the carb. Are you using a fuel filter?

Need to run a test or two before you start swapping out needles.

What is your cylinder compression?

[derrick81787]

I took the carb apart and looked at the jets, and they were clean and shiny. I am using a fuel filter, and I don't think there's any gunk in there or anything like that. I bought the gas in either January or February.

I have no idea what my compression is or how to find out. It starts on the first or second pull, though, if that means anything. I'm sorry but I'm completely new to this. I've only managed to figure out the carb by doing research online and taking it apart to see how it works.

[yaegerb]

here is the compression tester:

http://www.sears.com/craftsman-compr...p-00947089000P

Need to check that and ensure your compression is within spec.

Go here and download a manual for your 110

http://www.oscarmayer.net/atc/manuals/

I would also ensure the valves are adjusted appropriately. If that checks out then you can start messing with the carb.

[derrick81787]

Okay, I'm going to have to wait a couple days until I get paid to buy the compression tester, but I will definitely do that. The mechanic did check my compression, replace my valves, and adjust the timing though. I guess it's possible that he screwed it up, but worked when I first got it. That's why I'm so confused.

I'm reading about adjusting the valves in the manual. It sounds relatively simple. I'm not sure exactly where the valve adjustment covers are or if mine has the timing inspection hole, but everything else seems straight forward. I can probably handle doing that.

One other thing that I just thought of is that my spark arrester is missing. Would that affect anything with the carb?

Since I don't have the compression tester yet, let's just assume that compression is okay. If that's the case, does it sound like it probably is either the valves needing adjusted or the carb? If so, then that doesn't sound too bad. I'm really hoping that this is something that doesn't involve taking the engine apart.

Thanks for helping me out. I've been wanting to learn how to do basic engine work, so I guess this is giving me the opportunity to learn. I was just hoping to not have to do it so soon, haha.

[yaegerb]

No problem, we are here to help. if compression is within spec and your valves are adjusted properly then yes, I would say its either electrical or carb related.

Spark arrestor won't effect the carb.

I do have a question though...is the exhaust pipe tight against the exhaust flange...no play?

[sledcrazyinCT]

You mentioned the plug was black like it was running rich. You dropped the needle down a notch using the E clip which leans it out when running over say half throttle. Now the performance of your 110 has improved when you give it full throttle? Moving the needle clip position can make dramatic changes in how it runs. Since you got the 110 back how much has the outside temperature changed? Why couldn't the mechanic just rebuild the original carb? Sometimes the chinese carbs are just junk. Seems some people have good luck others say they can't get their machine to run right with the knock off carbs

[derrick81787]

Yeah, the exhaust pipe is tight.

This will be stupid if it's actually the problem, but I'm going to go to Autozone to pick up a new spark plug today. The mechanic didn't replace it because he said the old one was fine, but it seems to me that if the engine got rebuilt then I should spend an extra $3 on a spark plug. I filed on the old one a little bit and it ran a little better, so that might actually be the issue.

On a side note, I pulled on the starter to start it, and the rope broke off in my hand. That's just the way things have been going, haha.

sledcrazyinCT,

Yeah, it improved but it still wasn't as good as it should be. It was drivable, though, which up until this point it hadn't been.The temperature has changed quite a bit. It was in the 20s or so when I got it back, and yesterday it was 68 degrees and today it's in the 70s. I don't know why the mechanic couldn't just rebuild the carb. To be honest with you, I wasn't super impressed with the guy but there aren't many people around here who would work on an old 3 wheelers. Even the Honda mechanics said that they only go back to the 1990s. On the plus side, I have the original carb so I can still rebuild it myself if it comes to that.

[yaegerb]

Yeah, the exhaust pipe is tight.

This will be stupid if it's actually the problem, but I'm going to go to Autozone to pick up a new spark plug today. The mechanic didn't replace it because he said the old one was fine, but it seems to me that if the engine got rebuilt then I should spend an extra $3 on a spark plug. I filed on the old one a little bit and it ran a little better, so that might actually be the issue.

On a side note, I pulled on the starter to start it, and the rope broke off in my hand. That's just the way things have been going, haha.

sledcrazyinCT,

Yeah, it improved but it still wasn't as good as it should be. It was drivable, though, which up until this point it hadn't been.The temperature has changed quite a bit. It was in the 20s or so when I got it back, and yesterday it was 68 degrees and today it's in the 70s. I don't know why the mechanic couldn't just rebuild the carb. To be honest with you, I wasn't super impressed with the guy but there aren't many people around here who would work on an old 3 wheelers. Even the Honda mechanics said that they only go back to the 1990s. On the plus side, I have the original carb so I can still rebuild it myself if it comes to that.

If you need the carb rebuilt you can send it to me. PM me if interested.

[derrick81787]

Okay, I think that my carb adjustment and the new spark plug did the job. I put it back together, started it up, and drove it pretty hard for several minutes without any issues. Then, it started behaving weird and suddenly died while it was idling. I looked, and the bolts on the intake manifold were starting to back out. I tried to tighten them back, but evidently the threads are partially stripped. The bolts screw in just fine until it's time to tighten, but they just can't hold hardly any torque without backing out. These aren't the first threads to be stripped on this ATC, but they are the hardest ones to get to. Someone had put a standard nut instead of a metric nut on the chain tensioner, but I was easily able to recut those threads. One of the bolts holding the starter rope in was stripped, but I just replaced the bolt with a new one. However, these are the female threads in the cylinder head that are stripped.

I don't want to take the cylinder head off and redo all the engine adjustments for these if I don't have to. I honestly think that I would be in over my head and would have to spend money I don't have to have someone else put it back together for me. Do you think that something like this (http://www.amazon.com/Loctite-Form-A...ct_top?ie=UTF8) would work? Otherwise, I might be able to get a tap in there to tap the hole out slightly larger to 1/4 inch (6mm = 0.23622 inches) and use 1/4 inch bolts. I would love to use a Helicoil, but I can't get a drill in there while the cylinder head is still attached, and the Helicoil involves drilling and tapping it larger than 1/4 inch, so it would still be an option if the first rethreading attempt doesn't work.

What do you think? Does any of this sound like a possible solution? Thanks again.

[1979atc]

If you need to retap the threads on the head easiest way it to pull motor out of frame. Sounds like to me your points plate needs adjusted, I had a problem with my Atc 90 with a the same setup as this 110, would idle and run fine but at full throttle it would pop and try to die, then when you let off the throttle it would run fine and still idle. Could either be the points plate, points or your timing maybe off by a tooth, Or could be your carb.