backfiring

Ok so my Pitbike is a 2011 Pitster Pro frame and a 2006 Pitster Pro 125 motor. I just swapped the motor on to a newer frame a while ago. But I was out riding my pitbike on some trails and such for about 45 minutes. Nothing major. No jumping, dropping thrashing. Just trails. As I was riding on...

Hi there i really need help with my pit bike I've done a rebuild on it (done the piston and rings, timing chain, valve clearances) also cleaned out the carby, it was running before i did this and i also did rebuild it one before.. It does start but it is a bit hard to get running and everytime i...

just went to go for a ride, bike starts first kick still, but is backfiring when the throttle is snapped back, and will idle for about 10-20 seconds than splutter and die!!!! what could it be? i just put a new plug in, made no difference i was thinking vacumn leak? but cant find any...