I have got an air cooled tao tao 250 it was continuously spitting the chain and clunking as it did so. I upgraded the chain from 428 to 428H and changed the front sprocket from 15 to 13 tooth. The machine now has oodles of power and doesn't spit the chain however the son of a ratsinfratser will still stutter and clunk if I wot the throttle in any gear. Could I possibly have an output gear issue? Or is it a clutch issue?
Do I have a casset style trans or do I have to split the case to get in there?

 

I decided to replace the trans parts just cause I want to