Yamaha WR450F | Dirt

More than the Sum of its Parts

They say: "A potent off-road weapon."
We say: "We like how Yamaha thinks!"

To create the 2012 WR450F, Yamaha embraced “parts-bin engineering” rather than attempt to modify the YZ450F motocrosser for off-road use. Research confirmed that WR owners prefer woods and tight-trail riding and racing, and wanted a bike that felt lighter, had better front suspension and fuel-injection. Yamaha’s engineers felt the best solution was to add EFI to the current WR engine, and because the required systems already exist on the YFZ450 four-wheeler, the parts were already in the bin. The current YZ450F chassis wasn’t a candidate for a parts-bin raid, but the 2012 YZ250F’s redesigned aluminum chassis is totally modern with a great reputation for nimble handling. Raid parts-bin number two for one rolling chassis.

Not all the parts were existent. When needed, parts were redesigned to improve performance. For example, radiator capacity is up for better cooling, the connecting rod big end and bearing are wider, and the cam surfaces were revised for increased durability. The header pipe was extended and a resonator chamber added to boost midrange. A slim, new 2-gallon gas tank was fitted with the YZ450F’s fuel pump. The air filter, muffler, instrumentation and rear wheel all look like they came from a WR parts bin.

The engineers did a good job of packaging, as the EFI’s wiring is well hidden and the 450cc engine doesn’t look shoehorned into the 250’s chassis. Where they missed the mark was in their approach to meeting noise requirements by fitting a throttle stop that restricts the throttle butterfly. Naturally, that means performance in standard form is limited. Luckily, races like the River Ranch GNCC in Frostproof, Florida (where we tested the WR on private property), allow the legal removal of such restrictive parts.

With the throttle limiter and exhaust baffle removed, the bike didn’t sound much louder yet performance was dramatically improved. EFI adds instant response with zero hesitation, and the engine’s smooth low-end power helps find traction in loose soil and sand. There is plenty of over-rev, but the motor makes the bulk of its power in the midrange, so short-shifting is the best course of action. Clutch pull is moderate, and we found that the quick-adjust feature on the perch is needed as the lever feel changes as the clutch heats and cools. Once the restrictor was removed, our only real gripe was that the bike was not eager to start.

The choice of the YZ250F chassis was an inspired one. You forget you’re riding a 450—until you twist the throttle! This is one nimble bike with excellent turning manners. For tight woods racing the gear spacing is a tad wide, but it always pulls the gap.

The coup de grace is the WR's price: At $8090, it only costs $440 more than the previous model and still less than the unchanged, carbureted Honda CRF450X. When parts-bin engineering works, the result is better than the sum of the parts.

Tech Spec
Engine type|l-c single
Valve train|DOHC, 5v
Claimed horsepower|na
Claimed torque|na
Frame|Aluminum perimeter
Front suspension|Kayaba 48mm fork with adjustable spring preload, compression and rebound damping
Rear suspension|Kayaba shock with adjustable spring preload, compression and rebound damping
Front brake|Nissin two-piston caliper, 250mm disc
Rear brake|Nissin one-piston caliper, 245mm disc
Front tire|80/100-21 Dunlop Geomax MX51
Rear tire|120/90-18 Dunlop Geomax MX51
Seat height|37.8 in.
Wheelbase|57.7 in.
Fuel capacity|2.1 gal
Claimed curb weight|273 lbs.

VERDICT 4 out of 5 stars
Sharper and snappier, yet not much more expensive.

In order to power the EFI system, the WR’s stator output was increased from 120 to 160 watts. Unfortunately, the headlight is still only 35 watts.