Manufacturer Yamaha Successor Yamaha YZ450F Power 48.8 hp | Production 1974- Class Motocross | |
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Engine 250 cc single-cylinder, water-cooled, two-stroke, case reed | ||
The Yamaha YZ250 is a two-stroke motocross race bike made by Yamaha. It was launched in 1974 and has been regularly updated since. It is one of the only two-stroke bikes of this displacement to still be in production and release every year. For the Yz250 the top speed is 75mph.
Contents
Engine
The YZ250 has a 249 cc liquid-cooled two-stroke reed-valved engine with a YPVS exhaust valve for a wider spread of power. The engine produces a peak 48.8 horsepower (36.4 kW) at 8,800 rpm and 30.6 foot-pounds force (41.5 N·m) of torque at 7,500 rpm, with a 9,000 rpm redline (Motocross Action Magazine).
From 1974 through 1982 the engine sported a 70 mm bore and a 64 mm stroke to produce a displacement of 250 cc. In 1983, the bore was reduced to 68 mm and the stroke was increased to 68 mm producing a displacement of 247 cc. In 1999, the bore was further reduced to 66.4 mm and the stroke lengthened to 72 mm producing a displacement of 249 cc. The longer stroke engine resulted in a lower redline, slightly less top end power and greatly improved torque at lower RPM. 65 hp
Chassis
Since its introduction in 1974, the YZ250 has had a single backbone steel frame. For the 2005 model year, however, the YZ250 has a new frame made entirely from aluminum, which brought the dry weight down to 212 lb (96 kg), and more recently in 2010, to 211 lb. The bike has a swingarm rear suspension system with more than a foot of travel, as well as telescopic inverted forks with 11.8 inches (300 mm) of travel. Front and rear hydraulic disc brakes round out the YZ.
Championships
The YZ250 holds many championships: