The Kawasaki KX450 in production form is a great bike for the average consumer but it could stand to be a little more exciting in the engine department. Keefer and Pro Circuit team up to create a stage one engine kit that keeps cost low and excitement high.  

Keefer got a KX450 Pro Circuit stage one bike, which he rides in this video, and he breaks down the few simple changes that make a big difference. What are the differences to the stock KX450 and the KX450SR (Special Racer, Kawsaki’s “factory edition” bike). A pipe, piston, suspension, and a tuned ECU can go a long way.

“Out of all the 450s in 2026, Kawasaki KX450 seems to respond the best to very few modifications,” Keefer said.

“In all reality, you’re building kind of your own SR but with a little bit more meat in the mid-range and a little bit easier to ride,” he added.

Film/edit: Simon Cudby

Kawasaki KX450 Pro Circuit Stage One Bike