Ditch the XR650 motor and stick to the modern dirtbike engines. mid 50s in HP is what the XR will do, and that is probably what your 450/500 already is at with the (relatively) same reliability and less weight and better pick up.
Ditch the XR650 motor and stick to the modern dirtbike engines. mid 50s in HP is what the XR will do, and that is probably what your 450/500 already is at with the (relatively) same reliability and less weight and better pick up.
dave@MotoSix DOT com | MRA #31, WERA #311