Yamaha YZ250

The Yamaha YZ250 is a two-stroke motocross race bike made by Yamaha. It was launched in 1974 and has been updated regularly since, with new releases still arriving every year. The first machine used an air-cooled 250 cc two-stroke engine on a single backbone steel frame with a twin-shock swingarm, and a monoshock swingarm followed the next year. In 1982 the air-cooled motor gave way to a liquid-cooled, reed-valved two-stroke with a mechanically driven YPVS exhaust valve, and from 1999 a longer-stroke 249 cc engine traded a little top-end power for much better low-down torque, producing about 47 horsepower. An aluminum frame arrived for the 2005 model year, cutting dry weight to about 96 kilograms. US Dirt Bike magazine called it the last 250 two-stroke from Japan, and the model has won several AMA motocross, supercross and off-road national titles.