2003 660 Raptor ....i was riding my quad down the road and all sudden it started to slow down like somebody was grabbing the back of my grab bar. and all sudden it just it shut off on me while i was coasting, i just popped the clutch to turn it back on and coasted back to my place. and i started hearing knocking noises. i can post a video of the noise if needed. dont know if its a valve issue or what.... just would like some input if possible.. thank you..

 

When was the last time you adjusted your valves. Do you have oil in it. Stupid question but never know

 

You could have blown the engine up.