Yamaha, the Japanese motorcycle manufacturer, introduced the original YZ motocross bikes in the 1970s. The line was expanded, altered, and revised substantially over the years. The YZ 85 was introduced in 2002; the 2008 model was a carryover. The YZ 125 was introduced in 1974; it was revised in 2008. The 250 was also introduced in 1974; it too was revised in 2008, when it was among the last of the 250cc, two-stroke, off-road bikes manufactured. The 250F and YZ 450F were upgraded in 2008.
All five models are powered by liquid-cooled, single-cylinder, carbureted engines. The numbers tell you how powerful each engine is: the YZ 85 has a two-stroke engine that displaces 84 ccs, the two-stroke 125 displaces 124 ccs, the two-stroke 250 and four-stroke 250F displace 249 ccs, and the four-stroke 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. The models’ front suspensions are supplied by inverted forks with rebound damping; the rear suspension is a twin-sided swing arm with an adjustable spring preload and rebound damping. All have kick starters. The YZ 85 and 125 have six-speed transmissions; the YZ 250, 250F, and 450F have five-speed manual transmissions.
Yamaha makes a wide array of accessories for each model.