Yamaha Yz426f

Yamaha YZ426F

Defending the high ground

KING OF THE HILL, Top DOG, Numero Uno—all the while waiting for someone to come along and knock you off. Such is the predicament of Yamaha's YZ400F, the mid-sized four-stroke that creamed everybody the last two years. But hungry things like KTM's new competition Thumpers, the new and eagerly awaited (still!) Cannondale, specialty Singles such as the VOR, as well as regular premix-consuming motocrossers await.

With today’s MXers, even minor changes can make a big difference, sometimes the wrong way. To keep the consumer happy, though, you need a hook, so Yamaha took out the boring bar and—walla!—the YZ426F, a year2000 revitalization meant to add to the YZ’s already glowing reputation. But a 2mm bore job is not all that lurks within a bike that is visibly identical to its predecessor.

Addressing one of the YZ’s few weaknesses is the new top triple-clamp that roomifies the rider’s compartment. And a major change is a new 39mm FCR carb that is more compact, lighter and encloses the pumping mechanism to keep out dirt. Durability concerns also led to bulletproofing the transmission and crank, just to be safe.

The 426 retains the YZ’s unique— call it spastic in a good way—powerband, a perfect brew of explosiveness and tractability. For 2000, the jetting is crisper, which helps the motor resist bogging or hiccuping better than before. Power-wise, the engine is torquier (accented by the carb’s excellent performance) and the power hits a bit sooner. There is plenty of pop up top, as always, though the motor doesn’t seem as rev-happy as in the past.

In the suspension-tuning department, Yamaha went for a stiffer setup that holds the bike higher in its stroke, which, paradoxically, allows plusher action throughout the range of the travel. Okay, small-bump compliance may have taken a small step backward, but the 426 is better now in full-attack mode—you can hit things hard on the track and feel totally comfortable doing it. Bottoming resistance is improved, as well. Another fork-internals upgrade, switching steel innards to aluminum, gives the bike a much more flickable feel at the handlebars.

Though the competition has turned up the heat, Yamaha has responded with improvements to what was already the best MX Thumper ever.

Our upcoming four-stroke shootout should be a gas. Until then, the YZ426 is ready and waiting. —Jimmy Lewis