Need help with high-revving Kazuma!

[danjoneshistory]

I have a Kazuma (maybe 50cc?) that has a pedal shifter but no clutch cable. This seems standard. However, when the atv is in neutral, the engine revs like CRAZY and will pop a wheelie if I throw it in gear. While in gear, it has little to no power. Pressing on the accelerator doesn't do a thing. If I turn on the choke while in neutral, the engine dies completely.

Here's what I've tried:

Replacing the carburetor with a new one. No change.

Spraying around the connections between the carb and the engine with starter fluid, looking for an rpm change to see if air was leaking into it. No change.

Removing the throttle cable from the handlebar to see if it was too taut. No change.

Checked timing-- top dead center seems to match on the flywheel and the cam. Although this depends on the direction I rotate the engine. The only way to rotate it without the nut coming loose is to rotate it clockwise. When I do this, the engine timing seems right. But there is enough play in the chain that when I let it go slack, it may be out of time. This is likely normal, and I can't imagine this would be enough to cause this problem.

Any thoughts on what would cause an insane idle with no power under load?

I really need help. Thank you!

[JerryHawk250]

There shouldn't be any slack in the timing chain. It's possible the chain jumped a tooth. You've done everything else that eliminated carb and fuel issues.

[danjoneshistory]

Would a timing issue cause the engine to rev super high in neutral? I don't see how...

[JerryHawk250]

Originally Posted by danjoneshistory

Would a timing issue cause the engine to rev super high in neutral? I don't see how...

Yes if the timing is advanced.