I just raced my buddies ported and piped '06 CR250 (which will eat a 450). We were on pavement, he got the launch and I flew by him like he was sitting still about 40ft into the race and I pulled him hard the entire time. I'm running a stock cyl 350 with full drag porting, cpi inframes, and stock carbs. You wont have to worry if you race where you can hook up.