I took out the power valve and the read (how ever you spell it) valves were broken. So i bought some new ones. Installed it and there goes my bike. NOT it was going for around 20 min and then it died. I can't get it going again. I took out the carb and the power valve again. Put it back and still nothing. There's a load of oil coming out of my exhaust. Just now it started but it just died again. Can anyone think what’s wrong now?