1983 Honda 200s idles but won’t rev

[Hondaman428]

I am usually great with these things. Ok some history. I bought a Craigslist special. No history as I don’t trust the guy I got it from. It has been sitting for like 20 years. Was froze up. Only the rings though. Tore it apart and honed the cylinder and re ringed it and new gaskets. Lapped the valves. New springs in the ignition advance as those were rusted in half. It started right up. But won’t rev at all. Just seems choked out. (I cleaned the carb). I thought it might be a plugged exhaust. Nope. Checked all the timing. Cam is perfect and so is ignition. Great compression as well. It’s like a rev limiter. Like the timing is way off. I have re checked like 4 times. Lobes down. O is lined up with the mark on valve cover. Pin is at 11 and ignition is lined up as well.

[ATC King]

Honda didn't make the 200S in '83. Guess you mean just the ATC200.

Check the intake for restrictions.If the air box is attached to the frame, make certain the frame isn't plugged up.

Cleaning the carb isn't just taking apart what is held together with screws. It's knocking out all of the brass, which includes the needle jet, low and high speed air jets. Then it's really getting in there with things to get all the muck out, which usually includes a ultrasonic cleaner. Really nasty carbs aren't going to be cleaned with just a can of carb cleaner. There are small passages that carb cleaner alone isn't going to clear.

[Hondaman428]

You are right. 83 big red. The carb actually wasn’t too bad. After cleaning more than I can remember I was happy to see this carb. Although there still might be a clog. I guess I’ll try a carb off a 84 big red off a different trike. And I didn’t look into the frame. But I had the lid off. With and without brand new filter. Thanks!

[ATC King]

It seems like you've gone over most things, like the valve lash. Pretty much has to be the carb or the thing has CDI issues, like someone may have put a Chinese one on it at some point.

Of the oddest things out there, it has been documented that the inside of an OE exhaust header has collapsed and caused an issue like you describe. The OE header has two layers/double walled. If the inside layer has heavy rust/wear, it can collapse inward and block flow.

I wouldn't rule out the carb though, as I've seen many dirty carbs idle but not run past part throttle. Really getting in there to clean them takes a complete tear down, beyond what the majority of youtube vids is going to show or what most forum post will have. Got to use bolt extractors to get the low and high speed air jets out and drive that needle jet out with a punch. They're not normal service items, so have to get deep in there to reach the crud.

[Hondaman428]

Factory everything. But I think I have it figured out. Even though it makes great compression it is blowing back through the carb. So either timing is wrong (nope) or intake valve is leaking. But at tdc doing a compressed air leak test trough the spark plug hole it don’t leak!! It’s like the cam is wrong. The intake opens well before the piston is coming up for the power stroke. I have advanced and retarded the cam 2 teeth and it always blows back through the carb. Again. Cam timing is wrong or intake valve. I even thought the timing gear on the crank might of moved. Looks ok though. It does pull over a little funny. Lots of compression, but back feeds right before it gets compression. Fires right up first pull and idles. But bogs at around 2000. Like a rev limiter. It just has to be something with the intake timing. I almost made a makeshift degree wheel as it’s driving me nuts. I lapped the valves. New seals. And made sure they were straight. By no means am I new to any of this. I even took the muffler off. No difference.

[ATC King]

Maybe you're just overthinking it or getting tunnel vision.

Just walking away from it for a bit could sort it out.

[ATC200X4716]

If it idles it sounds like it's not too far off? Usually it's the other way around you can pop start something and keep it revving but dies at idle...puzzling Have you swapped to a good coil also? I had one once that worked, but like it saturated at RPM cause it would spit out the intake and die out, but start right back up again. Idled like a champ. Let us know what you continue to find.

[Hondaman428]

I think I found deeper problems. Seems the crank Bearings may be bad. Motor just turns over hard. Got it ripped apart again. Nothing wrong with the clutch side. Everything moves free. Not much left to rule out. Anyone know how hard it is to swap a hi-low sub trans on a regular 200s motor? Does the case have to be split for the output shaft? Or even the 84 shaft motor? I can find those motors everywhere.

[Hondaman428]

I think I found deeper problems. Seems the crank Bearings may be bad. Motor just turns over hard. Got it ripped apart again. Nothing wrong with the clutch side. Everything moves free. Not much left to rule out. Anyone know how hard it is to swap a hi-low sub trans on a regular 200s motor? Does the case have to be split for the output shaft? Or even the 84 shaft motor? I can find those motors everywhere.

Ok. Bearings are good. I found the problem. The starter gear behind the one way bearing was rubbing hard on the crankcase. The thrust washer between the cam gear and starter gear was in the wrong place. Just have to shake your head sometimes. Way better than splitting the case I guess.

[Hondaman428]

Pic of smoking gun.

[Hondaman428]

It seems like you've gone over most things, like the valve lash. Pretty much has to be the carb or the thing has CDI issues, like someone may have put a Chinese one on it at some point.

Of the oddest things out there, it has been documented that the inside of an OE exhaust header has collapsed and caused an issue like you describe. The OE header has two layers/double walled. If the inside layer has heavy rust/wear, it can collapse inward and block flow.

I wouldn't rule out the carb though, as I've seen many dirty carbs idle but not run past part throttle. Really getting in there to clean them takes a complete tear down, beyond what the majority of youtube vids is going to show or what most forum post will have. Got to use bolt extractors to get the low and high speed air jets out and drive that needle jet out with a punch. They're not normal service items, so have to get deep in there to reach the crud.

Well I’ll be. You were right. It was the exhaust header pipe. Never seen it before. This one had me stumped. I even sent a camera down and didn’t see it. Wish I would of listening sooner!!

[ATC King]

It's great that you found the issue and thanks for posting a picture of it.

There's a lot of information nuggets that get burried here, but I keep a list of where to find some of it. I'll be saving this one for sure.


It's kind of odd how the inside layer looks to be in decent shape right there though. Maybe extreme heat cycles, like taking a hot engine directly into a cold river/stream, can cause it. I notice it's right there in the bend when the tube is ovaled, so this could also be a manufacturing induced stress that causes a failure much later. The Honda ATC isn't the only brand and type of motorcycle/ATV that uses a double walled exhaust head pipe either.

I don't remember who else on here had that issue. I was thinking it was a more active member and maybe they would see this and chime in. It's certainly one of the less common problems, but next to intake tract blockage, exhaust blockage is something I've personally come across several times on all kinds of engines. It's usually the result of some insect or critter though.

Thanks again.

[Hondaman428]

Yea it was strange for sure. I thought the muffler was plugged. Seen that several times. The joys of buying something with no history. But like all problems in life there is a solution! And after those beers, sometimes stuff even gets fixed haha. Just glad to get er running again! Thanks again fellas!