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. The Empire Industries 54mm Billet throttle body and intake system flow’s a massive amount of air making your motor breathe better than ever. This is not an MX setup. It is intended for drag racing and the weekend warrior looking to smoke his buddies on the trail. 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 54mm billet throttle body. You will need to remove your stock air box to use the new high flow intake system. Fits 2009 to present! Free Shipping!