I have a Chinese 66cc 2 stroke engine on my bike, lately it's clutch had been acting up. When I'm riding along and then hit the breaks I pull in the clutch lever when I pull in the clutch lever the bike seems as if it is fighting against the engine, it has a pull and let go feel to it. Does anyone kno what the problem is? Also I pulled off the sprocket panel on the left hand side of the engine and the bolt that goes throughthe sprocket fell out. Why did it fall out? Is this bad?