I have a 2007crf450X that we completely stripped down. We took EVERYTHING off of it that made it a true X model (except the electric start). We shipped the motor off to PR2 and they completely modded the engine as much as they could, We put a Carbon Fiber Yoshimura exhaust, and a PR2 edition Vortex ignition on it so we could program the 110 octane fuel we were using. Im not even sure if my bike is legal or not in AMA motocross. But it sure is a sweet bike, and people are always turned around with a puzzled look when they here that beast start up with the electric start.