Yamaha, the Japanese motorcycle manufacturer, introduced the original YZ motocross bikes in the 1970s. In fact, Yamaha created the very first single-shock production motocross bike. The line was expanded, altered, and revised substantially over the years. The YZ 85 was in production from 2000 to 2008; the 2007 model was a carryover. The YZ 125 was introduced in 1974; it was revised in 2005, and that model was carried over in 2007. The 250 was also introduced in 1974; it was revised in 2006. The 250F was released in 2001 and produced until 2008; it was revised in 2006 and carried over for 2007. The YZ 450F was made between 2003 and 2008.
All five models are powered by four-stroke, air-cooled, single-cylinder, carbureted engines. The numbers tell you how powerful each engine is: the 85’s engine displaces 84 ccs, the 125 displaces 124 ccs, the 250 and 250F displace 244ccs, and the 450’s displacement is 449 ccs. Three models have reed valve setups; the 250F and 450F have dual overhead cams and Yamaha’s famous five-valve configuration. Disc brakes front and back provide stopping power. All models’ front suspension is supplied by inverted forks with rebound damping; the rear suspension is twin-sided swing with an adjustable spring preload and rebound damping. All have kick starters. The YZ 85 and 125 have six-speed transmissions; the other three models have five-speed manual trannies.
Riders could choose to customize their bikes with a wide array of accessories, including switching out the clutch lever and adding fork guards. All models competed successfully in motocross throughout the years in which they were produced.