my bros 300ex is having some trouble. IT is all stock except for kn filter. My dad and i adjusted the valves, b.c there was a clicking noise, backfiring, and absolutley no power at all ( blasters were eating it for dinner). We started it up, and 30secs. later it was making the noise again, so we adjusted the valves, and same thing happened. It sounds like the cam chain is slapping on the guide or something? does anyone know what the sound could be, or why the valves keep going out of adjustment??? any help, or info would be more than greatly appreciated.