Yamaha Yz250f
Yamaha YZ250F
CYCLE WORLD TEST
Legalized Cheater
JIMMY LEWIS
SNEAKY YAMAHA. JUST WHEN MOTOCROSS TRACKS WERE RECOVERING FROM FOUR-STROKE Fever, the Tuning Fork Company went and did it again, re-reading the AMA ru1ebook and redefining what Thumpers are capable of. And with a 250 of all things! We've heard all the chatter, the skeptics' contention that there is no way the new YZ250F will be competitive against 125cc two-strokes, and even if it was, who’d want to ride it? But we’ve also heard the comments from those who openly embrace the idea, riders of 125s and trailbikes who find fun in spite of dyno numbers. So who’s right, and where does this new 250 stand, anyway?
On the scales-and believe us, Yamaha valued the scales above all other tools in biftlding the 250F-the bike weighed just 224 pounds, 1 pound lighter than the current YZ250 twostroke. It is not a de-bored and -stroked YZ426F, but a unique machine, new from the ground up. Matching the 426 feature for feature, with each part sized for the 250 and then trimmed in every way for optimum weight. Light weight before all.
Getting to the specifics, the 250F is powered by a vastly oversquare, short-stroke engine, its 77.0 x 53.6mm cylinder residing under a five-valve dohc head. As on the 2001 YZ426F, titanium is the material of choice for the valves, specifically so that lighter valve springs could be employed, in turn giving better throttle response. Other Yamaha tricks include the use of a low-friction crankshaft, where the crank is not bound against the main bearings but is able to float freely, with 0.5 mm of side-to-side thrust. There’s also a balance shaft, which Yamaha is quick to point out makes up for its own weight by allowing other components to be made lighter.
The design of the cylinder head is all-new, and differs from the 426 in that the intake 3 and exhaust ports are arranged in a straight j line, meaning there isn't any redirection of gasses `til they hit the header pipe. The 37mm Keihin FCR carb is a shrink-wrapped version of the 426's 39mm pumper.
The chassis is similar in construction to that of the other YZs, but is 100 percent specific to the 250F. It utilizes the same basic high-tension steel main frame and aluminum subframe, but the backbone is lower thanks to the smaller motor. The swingarm and wheels are the same as the other YZs, and the suspension differs only in settings.
Yamaha’s design brief for the 250F clearly states that it is meant to compete against 125cc two-stroke motocrossers. Goals were lighter weight than a 250cc two-stroke, a hardhitting four-stroke powerplant that revved high yet had traditional Thumper tractability, and 125cc handling. A tall order. But three laps is all it took to realize the engineers not only reached their goals, they surpassed them in many ways.
The starting procedure is the usual find-TDC-and-kick, but as you can imagine, there isn’t much resistance from the little 250, even with 12.5:1 compression. Judging by noise alone, you’d hardly notice this isn’t a 400 or 426. Snap open the throttle in the pits and the lightning-quick manner in which the revs build gives you a hint, but the biggest giveaway is grabbing a handful out on the track. This thing revs to the moon!
The 250 doesn’t try to get away from you like the 426, it just picks up and moves with a bit more speed than a 125.
Right off idle there is barely enough torque to keep the motor running, let alone pull you out of a tum. The engine needs to be revved at all times, and like a 125 will bog if you’re not on it. But get it spinning, ride it like a 125, and it’s all about the right amount of power combined with the right amount of hook-up.
If you have any experience with 250cc four-stroke trailbikes, forget what you know because there are no similarities. Even more than the YZ400 and 426, the 250 combines the best features of twoand four-strokes. You might even call it a “three-stroke.”
And let us tell you about 13,500 rpm: Hello, screaming four-stroke Single! This is the rev-happiest dirtbike we’ve ever ridden, and the way it lightly bumps against the revlimiter makes working the power at the upper limit a pleasant experience. The ignition retards the timing before killing the spark so there isn’t an abrupt halt to the delivery, meaning you can literally use the limiter to help bang upshifts.
But how fast is it? Here’s the story: A 125cc two-stroke doesn’t stand a chance. Especially if the ground is slippery; then, a 250cc two-stroke is within the mini-Thumper’s grasp, even on a start straight. Again, the better the traction, the better it is for the two-stroke. In full loam, a 250cc twostroke will beat the 250F just like it would a 125. Peak power output is about the same as a 125cc two-stroke, but the 250cc four-stroke lays its power down better. It may have just a bit more on top, but it also has a longer pull, which means you have to shift less-almost half as much on the same track. It all adds up to faster laps, with less energy spent clutching and shifting. And we still haven’t told you about the best part! The 250F's handling is definitely one of the biggest surprises; it's as light-feeling as a 125 on the track. Due mostly to the minimal inertial mass inside the engine, flicking the bike around is simple. And direction changes in turns are even easier, cornpliments of the compression braking and tractable power delivery. Stability is first-rate. The overall layout is thin, and like any other YZ, the ergos happily matched all of our testers, regardless of size.
We also felt the suspension is the best of the entire YZ line. Ifs as plush as a YZ426F initially and seemed to resist bottoming better than the YZ125 and YZ250 we brought along for comparison. Despite our wide range of test riders, we never touched a clicker, front or rear. And that still isn’t even the best part!
The brakes are phenomenal. Because we’re used to the 426 being a bit heavy and not stopping like a two-stroke, it’s surprising how quickly you can haul the 250F down from speed. Just like a 250cc two-stroke, but again, the advantageous compression braking comes into play. Shifting is pretty good, and seems to get better with each ride. Clutch action is good and the clutch itself is apparently quite strong as it survived 25 startline drag races alongside our two-strokes.
Price is an issue with the 250F, but we’ll set you straight here, too. Its $5499 retail means you’ll be paying $500 more than for a YZ125. But add up the cost of pre-mix oil, a top-end every few months and a clutch or two, and you’ll save money in the long run. Especially if the 250F is as durable as its bigger brothers (read: indestructible). And it gets even better!
So, what’s the best part of the YZ250F? Well, it can be summed up in one word, and it isn’t “cheating,” which will be a word associated with this bike as long as racers are running it in the 125cc class. Though it fits in the rules for AMA competition, some other race bodies have already said it won’t be 125-legal. The word we’re talking about is “fun.” No, make that FUN! Because every rider who got on the F did way more laps than usual, and got off saying they had a blast. It’s the same syndrome that 200cc two-stroke enduro
YAMAHA YZ250F
$5499
bikes produce. It doesn't have too much power, which makes you feel like a hero because you're pinned all the time, stretching that throttle cable like the rocket rider you are! And as high-strung as the motor is, the friendly fourstroke nature still comes through loud and clear, especially in low-traction situations. More so even than the 426, the 250 is like a lightweight two-stroke with a four-stroke motor-just like bikes that guys have been trying to build in their garages for years. And not only is it fun, it's awfully competitive. Whether or not it wins races (and we're sure it will), it won over every rider that rode it. No question, Yamaha has built another Fantastic Thumper.
