If you have a built motor and a ported head, this is a must have for drag racing your CRF 450. The more air you can flow, the more horsepower you make. Empire Industries 54MM Billet Throttle Body ONLY for CRF 450 flows a massive amount of air making your motor breathe better than ever. This is not an MX setup. It is intended for drag race use only. You will need to use the stock fuel inlet, injector, idle adjuster, and map sensor off your stock throttle body. All the stock throttle body components easily bolt up to your new billet throttle body. Get yours today and start making horsepower!