Yamaha YZ250
 | |
| 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
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.[2] Front and rear hydraulic disc brakes round out the YZ.
Significant advances
| 2005 | Aluminium frame |
| 2006 | KYB SSS forks |
Championships
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
References
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Wikimedia Commons has media related to Yamaha YZ. |