A buddy of mine has a 90CC quad that the engine jammed up. He took the top end apart and it seemed to unjammed it's self. I check all out and crank feels good, piston did not seize so we put new rings in and a top gasket set in. Timed it and it was running like a top again. Well two days later it happened again. So I took off the magneto cover to verify it was jammed up again, I started turn the engine by hand backwards, it was tight but it was moving then something happened and all was back again. So we decided to take the whole engine apart expecting to see something major. But so far all looks good. My only theory now is the timing chain/tensioner is jamming some how and going backwards unjams it. Just not sure what to replace, I am going to change the timing chain, but the tension arm seem to be sloppy or is the spring loose. I was thinking about making a manual adjusting system that would not allow the adjuster to back-off. Just wondering if anyone else has had this happen and could point me in the right direction.

Thanks
NB

 

Its it a 90cc honda knock off type or what? What kind of trans auto or manual?