2002 YZ250F–JAN 2

2002 YZ250F–JAN 2


Blame it on Ernesto Fonseca. Ernie was so successful with the debut of Yamaha?s revolutionary YZ250F that the AMA didn?t post official results until the day before the second supercross round of 2001. For days, AMA officials debated the long-standing rule that allowed 250cc four-strokes in the 125cc class but couldn?t pull the plug on Yamaha?s multi-million-dollar program after just one race. Ernie was awarded 25 points for winning Anaheim One and would ultimately win the 125cc West championship, cementing the YZ250F as an unfair advantage, a “cheater” bike, in the minds of the AMA and two-stroke teams.

By the end of the 16-round supercross series, the controversial YZ250F had won half of the mains and half of the titles, so no less than two dozen 250Fs showed up at Glen Helen for the start of the 24-moto national series. Factory riders, aftermarket-team members and privateers alike made the jump to thumperdom in a week. At the start of every one of those 24 motos, 250Fs filled at least seven of the top ten positions, and the grumbling from the two-stroke camp became outright whining. And, with a win record of zero of 24 125cc motos, the YZ250F had a weight penalty attached to it for ?02. While a two-stroke 125 could weigh as little as 194 pounds, the YZ250F would have to weigh 216 pounds, or 22 more than the class standard.

Undaunted, Yamaha improved the new breed for ?02 and shaved another pound of weight. At this rate, Yamaha and the AMA will butt heads in eight years over this weight rule, but there are other ways to maintain the advantage, unfair or otherwise, until then.

SECOND VERSE, SAME AS?
Part of the YZF?s success came from its ability to out-accelerate two-strokes out of corners, especially slick, flat ones. Yamaha worked on improving that advantage for 2002 on two fronts. First, a new ignition map was refined to give the 250F more torque at lower revs. Indeed, the ?02 YZF does pull a bit harder through the lower midrange, but the difference doesn?t reach out and grab you. It still pulls from the basement to 12,000 rpm without any real hit, dip, spike or stutter, and it still has the ability to circulate any track with fewer shifts than a two-stroke.

Second, Yamaha worked long and hard on putting more of that smooth power to the ground. Suspension was almost completely reworked in the process. Yamaha transferred all of the suspension changes done to the YZ250 and YZ426 to the 250F, including a more-rigid swingarm, 5mm-longer shock, new linkage, two-piece fork piston and slick-coated fork tubes. These upgrades give the ?02 250F a big advantage over the ?01?and every ?02 125 we?ve tested. The fork is the best in its class; it reacts to stutter bumps better and doesn?t have any spike on slapper landings. It resists bottoming better than the ?01 but could use stiffer springs at the hands of Larry Ward or Rodrig Thain. We even like the YZF fork better than the YZ125?s.

Out back, the new shock setting not only gobbles up everything with more authority than the fork, it provides even more rear-wheel traction, both straight-line and side-bite. The 250F is the most stable machine in the 125 class, and it feels like its tires are somehow magnetic. The bike feels very planted at both ends and puts an end to the term “Yamahop.” And the high-low compression clickers let you tune the ride for every track, condition and riding style. We wonder if it would be this stable if it were lighter, but the handicappers at the AMA make this a moot point.

IF IT AIN?T BROKE?
New handlebars improve cornering a tad, and the improved suspension gives you more confidence to twist the throttle harder. The 250F is a hoot to throw around in corners, and handling is completely neutral. It?ll rail your intended line or careen off every berm with massive brakesliding, if that?s your thing. The 250F does carry a lot of momentum, though, so 125s can knife under it in tight turns. That?s how Mike Brown adapted to beat 250F pilots?run it in harder and slam them!

Yamaha addressed that, too, with a larger 245mm rear brake disc and more aggressive rear pads. Run it in harder, stomp on the more powerful brake and pivot off that ring-ding in front of you. Just don?t stall it. Yamaha made some improvements on the 250F?s weakest link, but it still isn?t cured of the high-compression starting blues. The ignition map that brings more torque also eases starting a bit, as does the larger hot-start circuit, but stalling the Yamaha still exacts a huge price in a race. Namely, you have to look down at the carb, find the hot-start knob, pull it, go through the mandatory start-drill.
That would be: pull decompressor, ease kicklever down until the piston is just past TDC, release decompressor, return kicklever to top, kick with no hand on the throttle. If it?s cold, use the choke and give the throttle two twists before The Drill. If you fell or stalled it, use the hot-start.

TRAIN OR TRAIL
Yamaha of Troy got Ernie and Nate Dog?s 250Fs down into the low teens in ?01, and we were hoping to see the day when a 250F bumped up against the 125cc limit of 194 pounds. With this new rule, you can only carve weight to 216, and it?s fairly easy to do. DSP?s Ti pipe and carbon airbox shave five pounds, so that leaves three pounds for Ti bolts and other carbon bits. Any more than that, and it?s definitely a cheater bike. Never mind that a 250F didn?t win a single 30-minute-plus-two-lap moto in ?01. Why? Weight! YZF guys got tired and got passed in every moto.
In the recent past, the 125cc class
hasn?t been known for producing a lot of dedicated trainers, with Ricky Carmichael being the exception. Since we can?t make the 250F lighter than it was last season, we?ll have to make ourselves stronger, longer.

BITS & PIECES
? Standard fork settings are 0.44Kg/mm spring, 140mm oil height, 12 clicks out on rebound, 13 on compression. Standard fork height is 5mm of tube above the top clamp. Run flush for more stability or at 10mm for tight tracks. With a 4.8Kg/mm spring, the shock wants 11 out on rebound, four clicks out on LSCD and 1.25 turns out on HSCD.
? Yamaha reworked the low-speed circuitry in the 37mm FCR2 carb, so jetting changed a little for ?02. Stock jetting is a 178 main (one size larger), 40 pilot (one size smaller), 105 leak jet, OBEKP needle in the fourth groove and 1.75 turns out on the airscrew. The 37mm Keihin is jetted perfectly and doesn?t pop or backfire. Go to a 180 main and 42 pilot when switching to an aftermarket muffler.
? Never slap a freshly-oiled airfilter in a YZF and immediately try to start it, as the carb will suck oil into its air passages and foul them. It won?t start until you clean the passages out with contact cleaner. It?s better to keep an oiled filter in a plastic bag in case you have to swap filters between particularly dusty motos.
? Standard gearing is 13/48, but many go to a 49 or 50 rear for tighter tracks.
? The manual recommends you clean and lube the fork oil and dust seal with lithium grease and lube the shock and linkage pivots with moly grease every three races. It also advises you tighten the sprocket bolts every race; we apply threadlock to them instead.

IS IT REALLY CHEATING?
Yamaha?s refined YZ250F has the best suspension in its class and the most power of a production “125.” Handling and turning are excellent, so good that it feels connected to the brainstem of the pilot. Brakes, controls and tires are top-shelf, but the YZ250F is not a cheater bike. Its weight will work the rider on really rough, undulating terrain and when charging hard through corners. In addition to heft, the YZF also has a big disadvantage in restarting after a fall or stall. Its advantages far outweigh the disadvantages in most situations, but those negatives can cost a lot in a money race.

As far as pro racing goes, the 2002 YZ250F is a cheated bike, not a cheater bike. It?s being cheated out of a relationship with Jenny Craig. As for the other 99 percent of us dirt bike enthusiasts, it?s the ultimate motocross bike for any class, especially age categories. Heck, throw a Thumper Racing 290cc kit in it and race it in the 250s, where it?ll just meet the 224-pound 500cc limit!

 

Comments are closed.