girlfriends bike. noise?loss of power?

[jf30cp]

Me and my girl both have motorized bikes with the happytime engines. we were riding along and she says,," stop! it made a horiffic noise now i have no power. so i rode it and it is pretty gutless to begin with. its hard to tell whats wrong because i am used to mine and mine has lots of power. so i checked for air leaks, tighted all the screws and bolts /also on carb. checked all gaskets. I dont know what to think. need a new plug? the plug looked good and if it was fouled it wouldnt run right? any ideas? I think the noise came from the chain hitting a tooth a bit off but i am up in arms
jeff

 

[stude13]

hi cp; if all alse fails, pull the head and ck. the bore. it might have gone lean for a sec.

 

[theblueboy]

I have the same problem! My bother was riding it and it didn't make a big noise,
it just loss power and now I can't even make it up a tiny hill and it doesn't go that fast
any more! What's the problem? Is the throttle messed up or the carburetor?
Help me! By the way, it is a 80cc upgraded motor.

 

[Bikeguy Joe]

I would check your intake gasket after looking at the spark plug. The plug should be dark brown to black.

 

[xlite]

If you have two bikes then you're in a good position to swap parts to see what's wrong. If you've swapped out everything that you can and problem stays with the block maybe time to just inverst in a new engine. Only $50-$75.

 

[Junster]

I just had the same problem. For me it was one of the pins in the piston that keep the rings from rotating. It came loose and put a deep gouge in the cylinder wall. Just pull the head and look in there. Hope that's not the problem. GL