I have a 1999 kx 250 and a don't know how to fix this problem. please help me!!! My bike starts and run fine at first. but when you run it around hard for a couple of laps it starts to rev up and down real fast with out me touching the gas. It is like small surges. please help with any advise. also when it starts reving you can not kill the bike with the kill switch. thanks bros.[/b]