It's not 2008. In fact, it's not even close. But that hasn't stopped Yamaha from delivering a nicely updated YZ-F to the hungry world of motocross. Welcome to the first test of the first bike from the future (of next year).
The 2007 Yamaha YZ250F was and is a solid bike. Consistent power with a smooth delivery kept it in the middle of almost all of our testers' rankings during shootout season. The handling and suspension were in the same boat, with most pilots happily riding the bike through the bumps and chop with some complaints on initial turning and settling. That's why we used it for a hop-up story (see "Stock to Sweet," August '07); it was easy to get along with stock but even easier to boost up to its potential for the more aggressive, faster racer. Almost before the ink was dry on that story, Yamaha was ready to deliver the '08, and after a week of testing, here's what we really think.
The single most noticeable improvement to the YZ250F on the track is the super-squeezing piston. By swapping last year's 12.5:1 compression-ratio piston with a 13.5:1 unit, Yamaha boosted power on the bike where it matters. The once mellow delivery is now enhanced with a healthy mid snap and newfound grunt. The bike is more than awakened from last year-from the bottom to upper mid, but still retains great tractability and stability while accelerating. Sometimes more power can damage a ride if it's not delivered properly-not so in the YZ-F's case. On top, the power behaves a bit like the '07, encouraging you to shift up to drop the revs to the reborn bottom and mid. Also, the piston skirt has been narrowed 4mm to drop some weight and reduce friction against the cylinder. These motors have been bulletproof for us in the past, and we expect the new piston to continue that trend... we'll see in a hundred hours or so. All in all, we love the new power and think it just might be the missing link the stock Yamaha needed.
Speaking of links, the new YZ-F features a revised linkage ratio under the shock that is helping keep all those new ponies in line out of the gate. There are other suspension changes as well. Stiffer springs front and rear, internal modifications to the compression circuit in the shock and shorter, lighter outer fork tubes all aim to improve the ride.
In our initial tests, the handling of the bike is almost mirroring last year's. The in-the-pit complaints of the bike resisting initial cornering movements are still mumbled, and we've experienced some unsettling in the rear over high-speed rolling bumps in corners. Basically, the bike likes to stand up. Sag adjustment is ultra-important as always, and we've found this bike wants a bit more than the recommended 100mm (our best has been between 103-105mm). This sounds like a small change, but its effect is huge. We're satisfied with the stiffer springs front and rear and will just keep looking for the perfect setup. One component of the handling is greatly improved: the tires. Bridgestone teamed up with Yamaha and developed the all-new M403 front and M404 rear that come mounted on this '08 YZ-F. They're solid. We rocked them on our '07 Stock to Sweet bike and were very impressed. We're working on dialing in the whole handling package for shootout time, so stay tuned (we know it's hard to be patient, but try).
The rest of the changes are basic yet nice. The carburetor features updated jetting; with a new double-taper needle the motor runs as clean as we've ever felt from a stock bike. The footpegs are now gigantic. With a 10mm-wider platform, they require an adjustment period for the shifter foot but are a nice pad nonetheless; they're also 5mm lower to open up the cockpit a bit. Internally, the bike's clutch finally has a single style of fiber clutch plate used throughout. Now you only have to buy one type, not two of one kind and seven of another. Thank you Yamaha, you're getting easier to maintain.