2001 Yamaha Dirtbikes

San Bernardino, June 19, 2000 -- When Yamaha came out with its YZ400F, it turned both the four-stroke and two-stroke worlds upside down -- there was a new Sheriff in town, and his name was Doug Henry: Piloting a once-thought-clunky four-stroke, Henry won the 1998 Mazda Trucks Motocross National Championship. Yamaha basked in the glory, winning the AMA's Mechanical Excellence award that year, proving themselves the first modern manufacturer that could make a competitive four-stroke racer. Other manufacturers were left scrambling, trying to design and produce a competitive "diesel" to compete head-to-head with Yamaha's new marvel -- as well as for the important California off-road market, which banned two-strokes.

In 1999, when the competition started to catch up, Yamaha simply bumped displacement up to 426 cubic centimeters and bought themselves some more time.
Enter year 2000. Four-stroke wars are heating up even more this year
(Cannondale, KTM, Husaberg and rumors about new super-thumpers from Kawasaki and Honda), and Yamaha intends to remain king of the diesel hill with an improved YZ426F, and an all-new baby super-thumper, the  YZ250F.
Now, don't confuse this mini-thumper with the two-stroke YZ250 -- it won't be replacing their smoker. Rather, the YZ250F was purpose-built to compete in the Supercross and Outdoor National series where it is allowed to compete against 125cc two-strokes. We have heard reports that one of the Yamaha of Troy racers is faster on the little thumper than on the YZ125, but word from Yamaha is that nobody but Doug Dubach and Ed Scheidler's boys have ever thrown a leg over the thing. Hmmm.

Doug Dubach flies Yamaha's New YZ250F

We had the opportunity to join the Yamaha boys at Glen Helen in San Bernardino, California, site of the first round of the AMA Outdoor Nationals and a portion of our own 250 Shootout, as they showed off their entire off-road line-up to the assembled press. Also on hand were Yamaha riders Doug Dubach and Dustin Nelson who would be putting in a few laps aboard the new bikes after tech-meister, Ed Scheidler, explained what was changed on each bike and why.

Two-Strokes
The smallest competition Yamaha, the YZ80, gets the "bold new graphics" treatment (BNG) and little else, unless you consider perforated graphics something to write home about. But, just north of the 80cc tiddler, the YZ125 received a number of changes to retain its status as one of the best motocross bikes to ever roll off a production line.

Yamaha's YZ125 underwent numerous changes to keep it at the front of the pack.

Both the YZ125 and YZ250 received numerous changes to keep them at the head of their respective pack. Both bikes (actually, all YZ's except for the YZ80) feature upgraded suspension with anti-stiction dust seals, outer tubes with low-friction internals and a lightweight aluminum piston rod. Also of significance is a new nylon spacer and a change in the bump rubber which are supposed to eliminate a metal-to-metal feel when bottoming the forks. In the rear, unsprung weight has been reduced by using a needle bearing on the lower mounting section, as well as an aluminum guide and a new bump rubber. Yamaha claims that there have been many such weight-savings throughout the bike and, even though a couple ounces here and there may not seem significant, in the aggregate, it adds up to a respectable amount.  Yamaha now employs the use of a "works-style" clutch lever design to allow on-the-fly adjustment as well as Excel rims which not only look cool, but are stronger than the previously used items. Brake upgrades include a new Nissin front master cylinder and the addition of a 250 mm floating disk (a Yamaha dirtbike first) to get braking power up into Honda's neighborhood.
The YZ250 Was Refined, Yamaha Hopes, to Perfection
Yamaha feels the most impressive feature about the new YZ125 is the motor they claim makes even more power than last year's version which, as it was, was no sleeper. Changes were made to the shape of the cylinder head as well as in the routing of the water which cools the top end. The exhaust ports have been re-worked and the YPVS ( Yamaha Power Valve System) has been changed "to improve air tightness." To compliment these changes, a new 38 mm Keihin carburetor has been installed to increase "low to top end punch without sacrificing any mid range power."
The YZ250 received a new cylinder head which features a higher compression ratio that works in concert with a new exhaust pipe to provide - according to Yamaha - more hit off the bottom as well as more over-rev. Internally there is a lighter piston pin which reduces reciprocating mass. Feeding the cylinder this year is a Keihin PWK38 carburetor with a new Throttle Position Sensor (TPS) and a repositioned power jet system. The TPS sends signals to a new 3-D mapped CDI that constantly adjusts ignition timing to suit conditions and, claims Yamaha, provides, "throttle response that is second to none."
Four Strokes

YZ250F: Coming soon to a Supercross near you!

The big news in Yamaha's line up is the YZ250F which we first reported on in our Daily News article and, from what we understand, has caught more than one manufacturer completely off guard. Not only is the 250F the first production motorcycle with titanium valves, it's also legal for competition in AMA 125 Supercross and the Outdoor National series. Remember Doug Henry and the YZ400F? The other manufacturers sure do. Yamaha calls their new 250F an "extreme performance four-stroke motocross bike" that's claimed to weigh less than most 250cc two-strokes. In addition to titanium valves (which will be featured on all of Yamaha's four-stroke  dirtbikes) the YZ250F is an all-new machine which only shares some suspension componentry with the other YZ models. It has liquid-cooling and a five-valve head with dual overhead cams. Yamaha claims the motor has "quick engine response and dramatic acceleration" and will rev to 13,500 rpm.

Dustin Nelson felt the '01 YZ426F actually had too much power this day at Glen Helen.

In addition to a YZ250F, Yamaha will also sell the WR250F alongside its motocross sibling. Changes from the YZ include a "specially designed" wide-ratio five-speed transmission, enduro-legal lighting, larger fuel tank, resettable tripmeter and an 18-inch rear wheel.
When queried about whether or not the new 250 four-stroke will steal many of their own 125cc two-stroke customers, Yamaha responded that it didn't think the YZ125 or YZ250 sales would be greatly effected. Instead, they expect that  people who feel the YZ426F is too much bike will opt for a 250F instead. They also expect the bike to take sales from a few other manufacturer's 400cc four-strokes and expect the bike to be just another option for Yamaha customers. One spokesman we talked to said that at a few dealerships, the day after they learned of the bike's existence, they sold their entire bike allocation, sight unseen.
While we didn't have the opportunity to ride any of Yamaha's new moto-weapons, from what we saw and heard, we ca

Is the WR250F Randy Hawkins' ticket back onto the podium?

nnot wait until we are sitting where Dr. Dubach and Dustin Nelson where sitting. Yamaha looks to have given itself some more breathing room in what has become increasingly tight classes these past few years. Lets see; an R1, an R6, a YZ426F and now a YZ250F. We've only just begun to get a glimpse at what other manufacturers are going to offer this coming year, but at this rate, it's going to take some very special motorcycles to eclipse the efforts of Yamaha.