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Yamaha WR 426F

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Make Model

Yamaha WR 426F

Year

2001 - 02

Engine

Four stroke, single cylinder, DOHC, 5 valve

Capacity

449 cc / 25.9 cu-in
Bore x Stroke 95 x 60.1 mm
Cooling System Lliquid cooled
Compression Ratio 12.5:1

Induction

39mm Keihin FCR39H carburetor

Ignition 

Digital CDI
Starting Kick

Max Power

58.1 hp / 42.4 kW @ 9000 rpm

Max Torque

49 Nm @ 7000 rpm

Transmission 

5 Speed 
Final Drive Chain

Front Suspension

46mm Kayaba inverted telescopic forks compression and rebound damping adjustable
Front Wheel Travel 300 mm / 11.8 in

Rear Suspension

Fully adjustable Kayaba single shock, 315mm wheel travel, separate high and low speed compression adjustment.
Rear Wheel Travel 315 mm / 12.4 in

Front Brakes

Single 250mm disc

Rear Brakes

Single 245mm disc

Front Tyre

80/100-21

Rear Tyre

110/90-18
Rake 27.2 °
Wheelbase 1490 mm / 58.7 in
Seat height  960 mm / 37.9 in
Ground Clearance 373 mm / 14.7 in

Dry Weight

114 kg / 251.3 lbs

Fuel Capacity 

8 Litres / 2.1 US gal

Torrance, California, January 18, 2001 -- We may live in a mad world, but it's also one where the inhabitants are incredibly lazy. Motorcyclists are no different, really. It's not that we can't do a top-end rebuild in under an hour using only a Leatherman, but we'd realy rather spend that time bench racing with a few friends and even more cold ones.
Similarly, when one of us wants to ride off-road, the common course of action is to buy a motocross bike and then spend a thousand dollars more on a flywheel weight, lights, suspension valving, exhaust systems and the like. We'd go through this hassle because a motocross bike does not make a good off-road bike, and most of the offerings from various manufacturers are little more than trail bikes.

For the 2001 model year, however, Yamaha has decided to yield to the horde of off-roadies and give 'em what they've been asking for: A trick thumper with all the technological updates of a moto bike replete with the minimal accouterments necessary for an effective off-road weapon.
As Yamaha's Terry Beal put it, "it's not just the YZs that we care about. We want to solidify our basis as the four-stroke leader."

The Year 2001 WR426F retains all the suspension tweaks, titanium valves, floationg front brake and other assorted goodies that found their way onto the Year 2001 YZ426F. Look closely and you'll also find the same high and low-speed compression adjusters on the rear shock, as well as the new needle bearing - plus a few additions to tailor performance for the bark-buster set.

In addition to all the YZ's goodies, the WR gets an 18-inch rear wheel, a larger 3.2 gallon fuel tank, a wide-ratio transmission and a stainless muffler that incorporates a spark arrestor. Oh, there's also the requisite headlamp and tail light assemblies. But there is still a decided lack of hand guards, presumably since each rider has their own personal preference and it's no use fitting things to a bike that will just as quickly be gathering dust in some dark corner of a storage shed.
So, is the WR426 really an add-gas-and-roost affair? Well, yeas and no. You could do that, but you'd be disapointed. You see, there's still this little matter of keeping the bike within certain noise limits that also limits a bike's performace. The WR comes fitted with a cover on the airbox, an insert in the muffler and a throttle stop which only allows you to open the throttle half way.
Fear not, however, as you can easily "fix" these "problems" just as easily as Yamaha did before turning us loose on their newest off-road weapon. Just keep in mind that these modifications are "for closed-course purposes only."

The airbox lid? This isn't the container where you'll be keeping your morning coffee, so you might as well put that lid in the parts bin. Same goes for the muffler insert, unless you want to be super stealthy and polite, of course. Then comes the little matter of the throttle stop. The stock length is 30mm from end to end. Cut this down to 23mm (leaving you to find some creative use for seven millimeters of threaded metal) and get on with your business, like we did.

After stepping off the YZ426F the week prior, the WR felt pretty mellow. Gone was the snap that is just dandy on a motocross course but would make you a poster boy for pain-relief pills in the off-road world. But, thankfully, it was not completely neutered of all its personality. The motor is mellow by moto standards, but that's a given. By off-road standards, this motor is just about perfect. It pulls with authority off the bottom into the sort of mid-range that will allow you to conquer just about anything nature has decided to place in front of you. Over-rev is, naturally, decent. But the power up high is pretty flat compared to the heaping helping of oomph you find in the mid-range. So, why bother with all those revs, then? Upshift the excellent tranny and keep the throttle open and the motor singing where it'll do the most good.

Initially, the suspension on our test bike was quite stiff. The motors had been broken in, but the forks and shock had not. This caused the first few miles to be rather harsh, especially on the hardpacked trails that were so abundant on this particular day. This no-doubt made for a few interesting momets while we got up to speed and familiarized ouself with the bike.

After a few whoop sections and drop-offs to loosen things up, the suspension started to work as it should, and proceeded to get better throughout the day. Subsequent rides have found us rather pleased with the boingers on this latest Yamaha.
You see, Yamaha did a smart thing by setting up the suspension for those of us on the Left Coast where
most of us magazine-types reside. East Coast set-ups may work fine out there, but they'll get you nothing but reviews telling readers how "soft and wallowy" a new bike is. By setting up the bike for something other than rock-crawling and mud-running, Yamaha effectively gave purchasers suspension that suits a broader range of applications. Definitely a good thing.

We left the front end pretty much stock, though we did increase compression damping by one click and played around with the rebound a bit, trying to keep the front end a bit more settled in rough, flat, fast corners. We left the rear end alone except for setting the sag at 100mm and, again, making a slight increase in compression damping.
In the slow-going, the suspension was a bit stiff. But in the sections that called for anything that put you into second gear and above, the WR was right at home. A bit of muscle is required to get the bike laid over and turning, so we often found ourselves taking a wider, sweeping line instead of staying tight. Faster section exhibited good stability and the bike never shook its head hard enough in the fast sections to cause any real concern.

The front brakes worked superbly, offering enough stopping power and feel for just about every situation. Rear brakes, meanwhile, took a while to bed in and required a heavy boot to get things locked up. The clutch offered good feel and modulation of power with minimal fade only on the toughest and nastiest of sections.
Sure, the bike could stand to shed a few pounds and the seat-tank junction is a bit awkWard. Also, we wouldn't mind a quart less fuel if it meant we could have a tank that's a bit thinner and a seat that's a touch longer and, perhaps, flatter for better rider movement.
In all, this bike represents a huge leap forward for not only Yamaha, but for off-road riders everywhere. It's a solid bike that carrys on the Yamaha four-stroke tradition proudly, closely resembling the moto brothers without sacrificing off-road prowess. It will be intriguing to see what Kawasaki and Honda come up with. But, until then, the bar has been raised.

Source Motorcycle.com