History of the Yamaha YZ450F

Yamaha YZ400F was the first modern production four-stroke motocross bike that was directly competitive against two-strokes. Yamaha introduced the YZ400F in production in 1998 after a successful AMA season in 1997. In 2000, Yamaha updated the YZ400F, increasing the displacement to 426 cc for greater power and throttle response, and then in 2003, the bike was updated to Yamaha YZ450F, also known as the bike that started the four-stroke dirt bike revolution.