I've raced a cr500 for years. Chuck and I raced together many times. They are fun. I mainly race mine with AHRMA. However last year I raced the last race of the mra season at HPR. Even with a cold seized motor I still did well! Mine has been highly modified over the years. 70+ rear wheel HP
16 tooth front sprocket, ported, pipe, 10 map vortex ignition, etc. etc. If they're built right the motors are pretty bullet proof.