Yamaha YZ250

From Wikipedia, the free encyclopedia
Jump to: navigation, search
YZ250
YZ250.jpg
Manufacturer Yamaha
Production 1974-present
Successor Yamaha YZ450F
Class Motocross
Engine 250 cc single-cylinder, water-cooled, two-stroke, case reed
Power 48.8 hp[1]
Torque 32 ft·lbf[1]
Transmission 5-speed
Suspension Monoshock, 12.8 inches travel
Brakes double disc
Tires Front: 80/100-21-51M ; Rear: 110/90-19-62M
Wheelbase 57.8 inches
Dimensions L: 85 inches
W: 32.5 inches
H: 51.2 inches
Seat height 39.1 inches
Weight 212 lb (96 kg) (dry)
Fuel capacity 2.1 US gallons
Related Yamaha YZ450F

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 about 95 mph unless geared other wise.

Engine[edit]

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. 47 hp

Chassis[edit]

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.[2] Front and rear hydraulic disc brakes round out the YZ.

Significant advances[edit]

2005 Aluminium frame
2006 KYB SSS forks

Championships[edit]

The YZ250 holds many championships:

  • 5 AMA National Motocross Titles.[3]
  • 9 AMA National Supercross Titles[3]
  • Most recently, Chad Reed rode the YZ250 to an AMA National Supercross title in 2004.[4]
  • 6-time AMA National Offroad Championships under the hands of Jason Raines. [5]
  • In 2014 Lewis Gregory rode the GL12 Racing YZ250 Yamaha to third in the newly formed EMX300 Championship. Winning the round at the Spanish GP on the way.

See also[edit]

References[edit]