A few months ago I got a 2 stroke motorized bike kit and put it on a bike. It worked great, and I enjoyed it for about a month and a half. Then, randomly it started messing up. It would idle mostly fine, and rev normally. Then, when I disengaged the clutch it wouldnt push the bike forward but give sudden jerks shaking the bike. If I increased throttle, it wouldnt give any power and eventually popping/backfiring, leaving a small puff of smoke in the middle of the engine. If I was lucky, it would sometimes pull me along and drive fine but if you worked it too hard it would backfire and die. After backfiring once, it would get almost worse right after, even then backfiring during idle. The spark plug sparked fine, the headbolts were all tightened to 12 lbs, and the fuel mixture is 20:1. I had a broken piston ring, ordered a new one plus a new head gasket and still no luck. There was a tiny score in the cylinder.