2005 Yamaha YZ250

:: By THE TESTING STAFF OF TRANSWORLD MOTOCROSS :: PHOTOS BY GARTH MILAN

The hard-working engineers at Yamaha Motor Corporation must not have gotten the memo about two-strokes falling by the wayside, because the extremely competitive YZ250 has been given a facelift of epic proportions for 2005.

In the ever-increasing four-stroke market that motocross has become, the new YZ250 is entering the class with its gloves up and ready to fight. Huge changes adorn the ’05 premier class entrant, most notably an aluminum frame that is a whopping 4.5 pounds lighter than the steel unit it replaces. Linked to the new frame is an updated fork and shock package, new ignition mapping, a lighter and more advanced swingarm, and a slew of other major changes that promise to keep Yamaha’s topmost two-stroke competitive with the brute power and incredible handling found on today’s thumpers.

AN ALL-NEW TWO-STROKE?!

Yep, that’s right-it’s no misprint. Just when you thought the days of fouling plugs and oozing black goo from your silencer were over, kick-ass two-strokes are back and better than ever!

Already blessed with one of, if not the most potent motors in its class, the YZ250 designers turned their attention towards lightening the bike and improving its handling for ’05. Their answer was to finally switch to the aluminum frame they’ve been teasing us with for years on bikes spotted at Japanese Nationals, and even raced with in Europe by Stefan Everts.

Yamaha’s first aluminum frame mixes casting, forging, and extrusion in its construction, all in hopes of avoiding the one major problem linked with aluminum framed motocross bikes in the past: increased rigidity and stiff handling. In a nutshell, their goal was to retain the same tendencies and characteristics of the tried and true steel frame but at the same time reap the benefits of the lighter aluminum material.

Using the AMA Method of weighing bikes, the new YZ tips the scales at a mere 217 pounds, meaning that it is over five pounds lighter than last year’s steel-framed model, and hovers right around the same weight as the works race machines that Chad Reed and David Vuillemin compete on, in stock form!

Beyond the frame changes lie plenty of other important updates, including a lighter Hydro-formed swingarm that also saves weight and provides betters handling. The front forks feature a slicker new coating, called “Kashima coating,” to minimize stiction, and coupled with a one-piece outer tube and an air/oil separation system, the 2005 forks cut friction nearly in half over last year’s models. In back, the shock gets a much-needed, stiffer 4.9 kg/mm spring rate, up from 4.7.

In the motor department, a newly-designed piston combined with revised ignition mapping and a rerouted exhaust pipe help the YZ remain competitive against its faster four-stroke competition.

There are plenty of additional updates found throughout the 2005 YZ250, most notably new CR-style front brake routing (thanks to Honda’s patent expiration) that allows for more efficient bleeding, a shorter hose, and an overall increase in performance. Another important and welcomed update comes in the form of an aluminum Renthal 790 YZ-bend handlebar, finally a stock item on the ’05.

If all that is still not enough, the new-generation YZ250 features tons of little changes like a stock white front number plate (switched from blue), a radiator shroud that requires just one size of T-handle to remove (the old one mixed Philips-head screws with 8mm hex head bolts), and even a new plastic compound that doesn’t turn white when creased. Everything adds up to make the YZ250 a much different bike in 2005, but the big question still remains: is it better?

ON THE TRACK

We’ll be honest from the beginning; of all the 2005 models we were most anxious to test, the YZ250 was right near the top of our list. The switch to an aluminum frame, combined with all of the other major changes and updates, had us itcching for our first outing on the ’05.

The TWMX testing staff took delivery of the YZ at the legendary, sandy Racetown 395 facility in the California desert. Our day of testing with Yamaha was hot; so hot that we were immediately forced to make some jetting changes to keep the YZ running smoothly.

Our pro test rider Pat Foster hit the track first, and came back very pleased with the revisions that Yamaha made. Just like most pros, power was Pat’s first and foremost test for the YZ, and he reported that the ’05 model passed with flying colors. Though just a tad sluggish off the very bottom, once the rpms climb toward the mid-range of the powerband, you had better be holding on tight! Already featuring one of the fastest motors in the business, we’re happy to report that the 2005 YZ250 is quicker than ever. All of our testers agreed that power is definitely not a problem when it comes to the YZ, as it enjoys sheer ass-kicking power that pulls heartily from bottom to top, with no flat spots to be had anywhere except right off the idle. This is the rare type of two-stroke motor that allows riders to become a little lazy with shifts but still enjoy plenty of forward momentum with a simple twist of the throttle.

One slight problem that we did encounter (and the hot temperatures didn’t help much here) was a slight pinging/knocking as the power climbed skyward. Though power wasn’t affected much from the detonation, it was still a bit bothersome and annoying.

As much as we hate to admit it, handling on the all-new 2005 YZ250 wasn’t quite what we had hoped for. Don’t get us wrong; the ’05 suspension improvements were all welcomed (especially the new, stiffer shock spring rating), and the YZ soaked up hits very well in everything from rolling whoop sections to big jump landings.

Where we had issues with the new frame was in the corners. Every test rider who threw a leg over the bike noticed that the ’05 YZ250 had a tendency to push its front end out of sharp corners and ruts, making steering the YZ a considerable chore compared to other bikes in its class. Similar to the first Honda CRF models, we’re pretty sure that the easy solution to the problem will come in the form of aftermarket offset triple clamps. Some testers took the advice of Yamaha technicians and scooted their weight farther forward to successfully combat the problem, but in our eyes a truly perfect bike shouldn’t require any position changes on the part of the rider to perform correctly.

Looking past the slight cornering problems we encountered during initial testing, the 2005 YZ250 is a great bike. The strong powerplant, incredibly light weight, and overall comfortable ride of the ’05 YZ make it a serious threat to the current wave of four-strokes taking over the class. If you still crave the flickable, easy-to-ride characteristics of a two-stroke (or just like the ‘braaap’ sound like we do!), then Yamaha has made the bike of your dreams. With a little work, we’re certain that the YZ250 can be cured of any cornering woes, making it a very real threat for upcoming shootout honors as well as a major consideration when deciding whether or not to give up on two-strokes.

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