Engine Trouble Why does my 2 stroke 80cc chinese bicycle motor lack power?

[21nafin]

I had an 80cc unbranded Chinese bicycle motor. When I first got it it was working fine. At one point the throttle body broke off the carburetor so I had to replace it. I replaced it with a racing carburetor which worked fine for well over 2 months. Later, it started seriously lacking power to the point where it wouldn't go up even the smallest of hills. I even hold the clutch in and rev the engine and it doesn't rev nearly as high as it should. I've cleaned the carburetor, adjusted the throttle cable, cleaned out the exhaust (even tried running it without an exhaust and still had the problem,) replaced the spark plug, and even drained the gas tank (which fuel flowed out of perfectly fine by the way,) and cleaned the petcock. When none of that helped, I replaced the engine. But I just replaced the engine itself, I didn't replace anything else with it. It's also worth noting that I replaced it with a 100cc engine rather than another 80cc engine. That didn't help anything, that only made it worse (it won't idle now.) So then I replaced the ignition coil, then I replaced the carburetor, with one specifically meant for 100cc motors. Neither of those helped either. What is my problem? I've basically replaced everything.

 

[Karl Snarl]

did you tune the carb to the engine?

 

[Aikaru]

I had an 80cc unbranded Chinese bicycle motor. When I first got it it was working fine. At one point the throttle body broke off the carburetor so I had to replace it. I replaced it with a racing carburetor which worked fine for well over 2 months. Later, it started seriously lacking power to the point where it wouldn't go up even the smallest of hills. I even hold the clutch in and rev the engine and it doesn't rev nearly as high as it should. I've cleaned the carburetor, adjusted the throttle cable, cleaned out the exhaust (even tried running it without an exhaust and still had the problem,) replaced the spark plug, and even drained the gas tank (which fuel flowed out of perfectly fine by the way,) and cleaned the petcock. When none of that helped, I replaced the engine. But I just replaced the engine itself, I didn't replace anything else with it. It's also worth noting that I replaced it with a 100cc engine rather than another 80cc engine. That didn't help anything, that only made it worse (it won't idle now.) So then I replaced the ignition coil, then I replaced the carburetor, with one specifically meant for 100cc motors. Neither of those helped either. What is my problem? I've basically replaced everything.

Okay so I had an issue literally identical to yours but I was able to fix it...

I assume by "Racing" carb you mean an HP carb with one of those fancy air filters, correct?

If so, I would just take it, and put it far far away.

The cheap chinese ripoffs you buy off of amazon that are "racing" carbs have no adjustments to control air to fuel mixture other than re-jetting.

The original "racing" carb is called a Dellorto, which has ACTUAL adjustments and is high quality.

Go back to an NT carb, fine tune it, and you'll have a properly working motor in no time

(P.S. if you bought an actual authentic dellorto, the high idle and low idle screws are in the float bowl along with the jet. You may just need to re-jet it. If you have one of those racing carbs off of amazon, trash it and get yourself an NT carb, or invest in a proper dellorto. Just know dellorto's require an insane amount of precision and patience to properly tune, but once you get it just right, they do have some benefit over a regular NT)