Yamaha WR250F

Pity the poor Yamaha dirtbike test rider. Oh, sure, it seems like a cushy enough assignment, taking a pay cheque and enjoying a comfortable benefit package, all for performing an activity that many people willingly pay good money to partake in - namely, spending the day in the saddle of a nice dirtbike.

But seven nice dirtbikes is another proposition altogether, and we've got to guess that after painstakingly evaluating and fine-tuning the YZ80, YZ125, YZ250, YZ250F, YZ426F and WR426F, the beleaguered Yamaha testers cried "uncle" when engineers rolled out yet another new competition model - the WR250F four-stroke offroad bike.

Implausible as it seems, it is possible to have too much of a good thing, even when that thing is dirt-bike riding. It's got to the point where even magazine testers are having trouble keeping up with the never-ending stream of new motorcycles (many of them blue).

Apparently Yamaha sensed this, for it sweetened the proposition of trying out its newest little thumper by arranging for its press introduction to occur at the South Carolina home of Team Yamaha's six-time American enduro champion Randy Hawkins, and inviting AMCN along.

Hawkins' property contains an ISDE-worthy grass track (with buffalo and llamas serving as unimpressed spectators), a red-clay motocross circuit, and an eight-kilometre test loop through some of the densest forest this side of a Christmas tree farm.

MINIMUM FRICTION
If you have absorbed any part of the recent flood of press on the YZ250F, then you're already fairly familiar with most aspects of the WR250F, though Yamaha did make several important changes to the motocrosser in the interest of off-road worthiness (see accompanying panel).

With the YZ250F, Yamaha wanted not a low-rpm plonker, but a thumper that screamed like a 125cc two-stroke, and despite its intended application, the WR is no different.

Like the motocrosser, it's got titanium valves (three intake, two exhaust), a light, short-skirted piston, a short-stroke engine, a ceramic composite-coated cylinder bore and a low-friction crankshaft.

The feathery valves allow for lighter-weight valve springs, and the entire combination makes for an engine with minimum friction and reciprocating mass - in other words, an engine that can rev to the moon (Yamaha claims over 13,000rpm).

Though it's 'just' a little 250, Yamaha saw fit to include a counter-balancer on the WR, and it resides at the front of the engine - just in front of and slightly above the crankshaft.

WORTHWHILE TRADE-OFF
Although including such a feature does make for an increase in the reciprocating weight, engineers felt that since the balancer reduces vibration, other parts of the motorcycle can subsequently be designed lighter than would otherwise be possible.

The only problem with designing an engine with such specific tolerances is just that - specificity. In other words, you can't just take a 426F bottom-end and throw on a smaller jug. The advantage, however, is that you can make a bike as light as possible, which is why there's a substantial weight difference between the two WRs, while KTM's 400 and 520EXCs share identical weights.

All of the updates that were made to the other competition bikes in Yamaha's 2001 line-up have been included on the new WR250F. This means there are needle bearings in the lower shock mount, a redesigned front-brake system and an easy-adjust clutch lever with a more subtle bend. Also, the fork now has a nylon spacer and updated bump rubber, as well as anti-suction dust seals, low-friction internals and a lightweight aluminium piston rod.

Apart from setting rear suspension preload and making a few clicks on the damping adjusters, I rode the WR in stock condition at Hawkins' house. The only real modification was the installation of a pair of GYTR hand guards.

A REAL SCREAMER
As expected, the WR250F is a screamer, a fact I confirmed while riding on Hawkins' grass track, periodically opting not to up-shift and instead let the bike rev. For absolute best results, it's better to stay in the meat of the power band (which is somewhere between midrange and top end), but for those situations when you are too busy (or lazy) to click into the next cog, the power is functional up there by the rev-limiter.

Off-road riding can be quite varied, so the WR would be useless if it had to be screamed in order to work competently. Hawkins took me out for a trail ride on my last day, during which I encountered a rather long, technical hill.

I hit the base with the bike singing up on the top end, but partway up, a bobble caused a loss in momentum. Thankfully, it was no problem to simply drop down into the midrange and grunt the rest of the way up the incline as if the error had never been committed.

That midrange is also useful in limited-traction situations or when picking your way through rocks and roots, as you can leave the bike a gear high and let the unloaded suspension do its job. This technique requires constant feathering of the clutch, but although we've heard stories of the odd YZ250F clutch failure, the worst I was able to get from the WR was a slight fade when abused.

A BIT MUCH?
About the only place you can't ride the WR is on the very bottom end. This won't bother advanced, intermediate or even some novice riders, all of whom rarely even visit that portion of the power spread. But for outright beginners, the bike may be a bit much, and these customers will be better off with a Honda XR250.

Another reason neophytes should steer clear of the 250F is that it lacks an electric starter, and even many faster racers will find themselves wishing for that magic button.

It may seem wimpy to wish for such comforts on a serious racebike (especially one with relatively low compression), and I'll admit that the WR can be kicked over without much effort (even without the aid of the compression release). But although it usually starts right up on the first or second kick, there are occasions on which a stalled 250F is quite reluctant to re-fire, even with the aid of the (normally helpful) hot-start button. If one of those occasions happens to be in a special test, it could ruin your score in a tight enduro.

BETTER SPREAD
The spread of the wide-ratio transmission is much better suited to off-road than the YZ's close-ratio gearbox, and it's also more necessary on a small-bore thumper like this than it is on a versatile 426.

That said, I plan to experiment in the future with different rear-sprocket sizes, as there are times when the gap between first and second seems a bit much.

Yamaha did a good job of choosing suspension settings that are a decent compromise between fast desert conditions and slow enduro applications, as the WR rarely seems out of place. Heavier riders should opt for stiffer spring rates, and enduro riders may prefer lighter valving, but for the most part, the 250F absorbs obstacles with aplomb.

The feel of the bike is also quite good, with a nice, flat layout that allows the rider to move easily back and forth. The only complaint here is that the large tank extends further back on the frame than does the YZ's, and some riders will wish they could get their weight further forward.

Grievances are few and far between with the WR250F. First, a small one: some riders will find that their left heel rubs on the kickstand spring.

Now, the big one: this bike is too loud! The sound level is acceptable with the muffler's baffle in place, but once it's removed (which is how most people will run it), the WR emits a bark that is downright annoying. Granted, it's a nice sound, but there's just too darned much of it.

LOVE AT FIRST RIDE
Apart from that, I'm in love with Yamaha's latest offering. The WR250F is fast, well-suspended and light.

Yes, the weight of the off-road paraphernalia is noticeable, but the bike can still be flicked through the trees with less effort than just about anything else out there, a trait that becomes more and more valuable as the kilomteres pile up and the energy runs out.

Just like the YZ250F, the WR250F makes the average rider feel like a hero, and you can't ask much more from a bike than that. Give those Yamaha test riders a raise!

Chris Jonnum. Photos: Joe Bonnello

THE RIGHT FORMULA

The specialist motorcycle press has consistently applauded Yamaha - both for what it does and for what it doesn't do when it comes to dirtbikes.

What it does is use as a base its latest, top-level motocross models (in this case, the brand-new, much-heralded YZ250F four-stroke). What it doesn't do is ruin said motocrosser by overly de-tuning it and/or replacing trick lightweight components with cheesy, heavy parts.

Of course, engineers aren't stupid, and finding the proper formula is not as easy as it sounds. Simply hanging a headlight on a motocrosser and calling it an enduro bike doesn't cut it, so Yamaha increases its chances for success by beginning with a strong basic concept: bring YZ technology to the off-road market.

That sounds like a throw-away marketing phrase, but following it to the letter insures that the most cutting-edge equipment is spec'd and that the particular needs of the off-road enthusiast are considered.

With Yamaha of Troy's Ernesto Fonseca (pictured above) consistently winning rounds in the 125cc EA Sports AMA Supercross Series, there's not much question as to whether Yamaha met the first part of its goal: obviously, this titanium-valved 250cc four-stroke is the absolute latest in motocross technology.

But what do the tuning-fork folks do to complete the second half of their goal? Well, for starters, Yamaha does indeed hang a headlight on the bike. It also swaps the stubby motocross mudguard with a unit that drops down a bit in the rear and incorporates a 12-volt, five-watt tail light.

In order to run the lights, a lighting coil is used, along with a heavier flywheel. A voltage regulator and a WR-specific ignition are also utilised. Yamaha has also altered the timing on the cams by one tooth for better bottom-end grunt, just as it does with the WR426F (this modification can easily be reversed if so desired).

In addition, the ratio of the five-speed transmission is widened in comparison to the YZ.

Like the engine, the suspension has been refocussed for slow going over gnarly terrain, with the valving lightened up a bit (the same 4.31 and 47.0 fork and shock springs, respectively, as the YZ are utilised).

For the longer distances covered in the off-road world, Yamaha mounts the same 12lt fuel tank (including 1.59lt reserve) that is used on the WR426F.

The larger cell extends back on the frame further than the YZ's so a shorter seat is also utilised.

To accurately monitor those longer distances covered, a resettable odometer hides behind the front numberplate, and for when you're resting after covering those distances, there's a left-side sidestand.

To meet forestry regulations, a spark arrestor is added to the WR's stainless-steel muffler, as is a removable sound baffle. Also, Yamaha installs an anti-backfire valve on the WR, in consideration of the downhills and engine-braking deceleration situations that abound off-road.

Yamaha uses an 18-inch rear rim instead of the YZ's 19-incher, to reduce the possibility of pinch-flatting a tyre on a rock. Also, an aluminium guard is added to protect the left side of the WR's engine from rocks, joining the aluminium right-side guard and the resin skid plate that are shared with the YZ.

The 52-tooth rear sprocket is steel instead of aluminium, so it doesn't get bent on rocks, and the chain that wraps around it has O-ring seals to better resist the water and mud of off-road riding.

And for those situations when you find yourself slowly slogging up a slippery incline, the larger-capacity radiator (11 tubes instead of the YZ's 10) should help keep the bike from boiling over (the rider himself is on his own, however).