Sputtering and backfiring at any rpm above idle? Need help with my trx200

[BarnBoy]

1984 Honda trx200, same drive train as 84 atc200es. Let me list for you the things I have checked, tested, cleaned or rebuilt:

Carb...duh...well, not so much. 2 different OEM carbs, rebuilt with a shindy kit and cleaned, ultrasonic or carb cleaner, shindy jets, oem jets, every possible combination

Brand new air filter

New intake manifold/insulator

New fuel line and filter

Checked tank petcock

Checked stator

Checked ignition timing

Checked valve timing

Checked ignition coil

Tested with another OEM used CDI

Removed exhaust to eliminate chance of it being plugged

New spark plug

Compression @ 155 psi

Things I have not checked:

Carb float level (i don't see how itd be off on both carbs though)

Valve clearance

And it still runs rich (wet black plug), pops, sputters, and backfires when at any rpm above idle. No matter how I adjust the carb, where the needle is, etc. Sick and tired of messing with it...maybe someone can give me a tip on something I may have missed.

[kb0nly]

I would suggest check the valves, when cold, and make sure they are right. As for the sputtering and backfiring above idle, did you go through the timing advancer? The springs on it get weak, which causes the timing to not advance on acceleration. I had this problem on my 200ES, very similar symptoms, running rich and pops and sputters above idle. I went through the carb and such and put a timing light on it and found out the timing was stuck in one spot, i had a new set of springs for the advancer stashed away and put them on and that fixed it up. Also take the advancer out, take it apart, clean it, oil all the moving parts, make sure the weights move freely, etc.

If neither of those help... then i am in the same place you are scratching my head.

[Scootertrash]

Carb float level is something I check with every carb cleaning/refurb. The bowl is off and it takes a minute or two. It is kind of important to have it right, I don't understand why people don't take the small amount of time to check it.

Valve clearance is a regular maintenance item and should be checked as well when having issues with the way a machine runs.

Have you run through the complete jetting procedure? If nothing you are doing fixes the problem you should be going back and if not starting from step 1, starting from the point where you know everything is working properly and making sure you didn't miss a step, forget something, or overlook some small thing that could be causing the issues(s).

It can be very frustrating and patience is the key. If you start getting frustrated and /or angry, walk away for an hour or a day to clear your head, it can work wonders sometimes.

[BarnBoy]

I would suggest check the valves, when cold, and make sure they are right. As for the sputtering and backfiring above idle, did you go through the timing advancer? The springs on it get weak, which causes the timing to not advance on acceleration. I had this problem on my 200ES, very similar symptoms, running rich and pops and sputters above idle. I went through the carb and such and put a timing light on it and found out the timing was stuck in one spot, i had a new set of springs for the advancer stashed away and put them on and that fixed it up. Also take the advancer out, take it apart, clean it, oil all the moving parts, make sure the weights move freely, etc.

If neither of those help... then i am in the same place you are scratching my head.

Ok, I will check the valves.

I did go through the advancer, but didnt diassemble it. The springs looked like they were in good shape. Dont have a timing light so I havent checked that....but all the marks line up, it would be pretty obvious if it was off a tooth or whatever.

[BarnBoy]

Carb float level is something I check with every carb cleaning/refurb. The bowl is off and it takes a minute or two. It is kind of important to have it right, I don't understand why people don't take the small amount of time to check it.

Valve clearance is a regular maintenance item and should be checked as well when having issues with the way a machine runs.

Have you run through the complete jetting procedure? If nothing you are doing fixes the problem you should be going back and if not starting from step 1, starting from the point where you know everything is working properly and making sure you didn't miss a step, forget something, or overlook some small thing that could be causing the issues(s).

It can be very frustrating and patience is the key. If you start getting frustrated and /or angry, walk away for an hour or a day to clear your head, it can work wonders sometimes.

What is the measurement and where do I measure from? I didnt bother because its got a plastic float...Figured theres not much adjusting it. Could be wrong though, Ive never had that issue.

Will check valve clearance.

I have not run through the jetting procedure. I bought the bike as a non runner. I havent modified anything, I guess that doesent mean a previous owner could have..... Im running stock size jets, I tried the new ones in the Shindy kit and the old OE ones, no difference. I baffled because it did this with 2 carbs. The 2nd was one I had on a 185 years ago and never remember any issues with it.....

I work on this POS in spurts lol. Bought it early spring, jacked with it till I couldnt take any more, let it sit for a month, came back for a few weeks, frustrated because it still wasnt working, away for another month or 2. But I'm sick of it in my way, I wanna fix and sell it.

[ATC King]

You don't have to fix it to sell it to me. I'll buy it cheap so you don't have to worry about it anymore.



Have you tried running it without the lid on the air filter box?

[BarnBoy]

You don't have to fix it to sell it to me. I'll buy it cheap so you don't have to worry about it anymore.



Have you tried running it without the lid on the air filter box?

Yep. And without the air filter, and pulled the muffler to make sure it wasn't plugged, and done almost everything else I can think of. You're not that far away, come on over lol

[ATC King]

Do you have another head pipe to try?

The ATC ones are two layers, a pipe inside a pipe. A while back, someone posted they were having some issues and it turned out that the inside layer had rusted and collapsed, at least partially anyway.

Dual wall head pipes aren't uncommon, there are OEM motorcycle ones built that way too.

[BarnBoy]

Do you have another head pipe to try?

The ATC ones are two layers, a pipe inside a pipe. A while back, someone posted they were having some issues and it turned out that the inside layer had rusted and collapsed, at least partially anyway.

Dual wall head pipes aren't uncommon, there are OEM motorcycle ones built that way too.

Yes, I didn't think about that. It is a trx200 but same as the 200es Big Red drive train wise.

[BarnBoy]

I think I got it figured out....I'm gonna sound like an idiot lol. I'm pretty sure my issue was simply a tight intake valve. This sum buck runs 10x better after adjusting the valves. Who'd have thought. Goes to show its the simple things sometimes, I was just too lazy to check it until today. Just wanted to update for posterity.