Yamaha WR450F

Yamaha WR450F

250px 2010 Yamaha WR450F
Manufacturer	Yamaha Motor Company
Parent company	Yamaha Corporation
Class	Enduro
Engine	Single-cylinder, DOHC, Multivalve, water-cooled, four-stroke
Transmission	5-speed, wet clutch, chain drive
Suspension	Front: Kayaba inverted fork; fully adjustable Rear: single shock; fully adjustable
Brakes	Hydraulic single disc brakes

The Yamaha WR450F is an off-road motorcycle made by Yamaha Motor Company. It currently has a 450 cc (27 cu in) liquid-cooled single-cylinder engine. First offered in 1998 at 400cc, it shared many components and design concepts with the YZ400F motocross model. It is basically the racing YZ450F detuned slightly for more controllable power, with a headlight and lighting coil, softer suspension, a kickstand, lower noise specifications, larger radiators and lower emissions. The WR in the name indicates a wide-ratio gear box common to most enduro or trail bikes and stands in contrast to the close-ratio gearbox essential to a motocross racer. Over the years the WR has benefited from the advances made in the YZ motocross version gaining displacement and advancements such as an aluminum frame and improved suspension.

First Generation WR400F

Production	1998-1999
Successor	WR426F
Engine	Five-valve, 400 cc
Fuel capacity	3.2 US gal (12 L; 2.7 imp gal)

First generation: WR400F - 1998-2000

Yamaha introduced the WR 400F in 1998. The 400F is a four-stroke off-road motorcycle produced for three years, beginning in 1998 and ending in 2000 (only the YZ was upgraded to 426 cc in 2000). The WR400F is related to the YZ400F, a motocross model. Like the YZ400, it was considered to be a groundbreaking model in motorcycle history, ushering in the four-stroke era which ended the dominance of two-stroke engines in motocross and offroad racing. While many modern performance four-stroke dirt bikes have been criticized for excessive rebuild costs and short motor lifespans, the Yamaha WR400F has an impressive record of reliability, often attributed to its steel valves and generous oil capacity.

Second Generation WR426F

Production	2001-2003
Predecessor	WR400F
Successor	WR450F
Engine	Titanium five-valve, 426 cc, 95mm x 60.1mm stroke, compression ratio 12.5:1
Brakes	250mm front, 245mm rear
Wheelbase	58.7 in (1,490 mm)
Fuel capacity	3.2 US gal (12 L; 2.7 imp gal)

Second generation: WR426F - 2001-2002

In 2001 the WR400F's engine was uprated and it became the WR426F increasing the displacement to 426 cc (26.0 cu in) for greater power and throttle response. A beefier YZ style clutch basket and plates than those on the WR400 improved clutch performance. Frame geometry was identical to the 2002 YZ250 and YZ426F with a 58.7 inch wheelbase and 14.7 inches of ground clearance. This was the last WR to make use of a manual compression release for stating.

Third Generation WR450F

Predecessor	WR426F
Engine	Titanium five-valve, 449 cc, 95mm x 63.4mm stroke, compression ratio 12.3:1
Frame type	Aluminum after 2007
Suspension	Front: 11.8 in (300 mm) travel Rear: 11.6-in travel
Brakes	Front: 250 mm disc Rear: 245 mm disc
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

Third generation: Yamaha WR450F - 2003-2014

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.

Fourth Generation WR450F

Predecessor	WR450F
Engine	Fuel-injected, Titanium four-valve, 97.0 mm x 60.8 mm stroke, compression ratio 12.5:1
Suspension	Front: 12.2 in (310 mm) travel Rear: 12.5 in (318 mm) travel
Brakes	Front: 270 mm disc Rear: 245 mm disc
Tires	Front: 80/100-21 51M Rear: 120/90-18 64M
Wheelbase	57.7 in (1,466 mm)
Dimensions	L: 85.2 in (2,164 mm) W: 32.5 in (826 mm) H: 50.4 in (1,280 mm)
Seat height	38.0 in (965 mm)
Weight	271 lb (123 kg) - 249 lb (113 kg) (dry)
Fuel capacity	2.0 US gal (7.6 L; 1.7 imp gal)
Related	Yamaha YZ250FX

Fourth generation: Yamaha WR450F - since 2015

For 2014 The WR was given the reverse slant, 4-valve, fuel injected motor previously available since 2010 in the YZ450F. For 2016, Yamaha produced the YX450FX a more Enduro competition oriented version of the off-road 450 utilizing more design elements of the motocross model such as stiffer suspension and a close ratio gear box while maintaining electric start and the 18" rear wheel.