Since 2003
| Predecessor | WR426F |
|---|---|
| Engine | single-cylinder 449 cc (27.4 cu in) liquid-cooled DOHC four-stroke 5 titanium valves, 95.0 mm x 63.4 mm stroke, compression ratio 12.3:1 |
| Transmission | 5-speed, wet clutch, chain drive |
| Frame type | Aluminum after 2007 |
| Suspension |
Front: inverted fork; fully adjustable, 11.8 in (300 mm) travel |
| Brakes | Front: hydraulic single disc brake, 250 mm Rear: hydraulic single disc brake, 245 mm |
| Tires | Front: 80/100-21 51M Rear: 110/100-18 64M |
| Wheelbase | 58.5 in (1,486 mm) |
| Dimensions | L 85.6 in (2,174 mm) W 32.5 in (826 mm) H 51 in (1,295 mm) |
| Seat height | 38.6 in (980 mm) |
| Weight | 244 lb (111 kg) - 249 lb (113 kg) (dry) |
| Fuel capacity | 2.6 US gal (9.8 l; 2.2 imp gal) before 2005, 2.1 US gal (7.9 L) after 2005 |
| Related | YZ450F, WR250F |
For 2003, the engine displacement was increased to 449 cc, the fuel tank was reduced to 2.6 gallons and the bike came with an electric starter as standard equipment. The 2005 WR weighed in at 244 pounds dry, the seat height was reduced to 38 inches and the fuel tank was decreased to 2.1 gallons. The 2006 WR weighed in at 249 pounds dry and produced 42 horsepower. For 2007, the WR gained restyled plastics and an aluminum frame dropping the weight from 249 to 246 pounds. . Over much of its life the weight of the WR450F has remained fairly constant ranging from 244 to 249 pounds dry weight.
A limited production version of the WR450F was the WR450F 2-Trac, which featured 2-wheel drive. The gearbox output sprocket drove a short, fully enclosed chain to a pump, which in turn pushed the oil to the front hub via the pipe and back via the parallel pipe. A maximum of 15% of the power was transmitted to the front wheel at any time. Yamaha planned on building 250 2-Tracs in 2004, but only a few were built, which were used for enduro racing.
Read more about this topic: WR450F, Third Generation: Yamaha WR450F