GP’s Classic Steel #72: 2001 YZ250F

For this week’s GP’s Classic Steel we are going to take a look back at the machine that drove the nail into the coffin of the modern two-stroke, the 2001 Yamaha YZ250F.

For this week’s GP’s Classic Steel we are going to take a look back at the machine that drove the nail into the coffin of the modern two-stroke, the 2001 Yamaha YZ250F.

Perhaps no bike in history has had as profound of an affect on the sport of motocross as the 2001 Yamaha YZ250F. Fair or not, Yamaha deserves credit for taking an idea no one else thought would work and starting a revolution.

Today, the motocross world is awash in high-tech thumpers. The fuel-injected valve and cam wonders offer incredible performance and awesome ridability, all in a package nearly anyone can make use of. They are the do-it-all off-road machines for the modern age. In 2013, the four-stroke is King.

Life begins at 13,500 rpms: The super short stroke 249cc mill in the YZ250F looked to be a carbon copy of its YZ426F big brother, but the two actually shared no parts in common. Even with all its additional running gear, the remarkable YZ250F mill actually weighed a pound less that the YZ250 two-stroke power plant.

The interesting thing to note, however, is that the same thing could have been said about the two-stroke forty years earlier. Prior to the mid-sixties, big booming thumpers ruled the off-road world. Massive BSA’s, Husky’s and Lito’s thundered through the hills and valley’s of Europe, carrying riders like Sten Lundin and Jeff Smith to motocross glory. These big, powerful machines were a handful for even the most talented men to handle and required a great deal of skill to master.

None the wiser: The new YZ250F looked so much like its big brother that Yamaha actually had no need to disguise it in pre-production testing. Prior to its introduction, Doug Dubach spent the winter testing the 250F all throughout Southern California with the simple addition of YZ426F decals.

Then along came the two-stroke, the new miracle of the modern age. These incredibly light and powerful machines made quick work of the old school four-bangers and swept through the sport like wild fire. By end of the sixties, the four-stroke had been relegated to bit player status, as every manufacturer switched to making high-performance oil-burners. 

Father of the modern racing four-stroke: The original YZ400F was the brainchild of this man,  Yoshiharu Nakayama. Nakayama, a Yamaha engineer, designed and built the first YZ400F prototype in his spare time. Incredibly, three years later he would do it all over again with his design for the amazing YZ250F.

What would follow would be forty years of two-stroke dominance. Further innovations like reed-valves, liquid cooling and variable exhaust ports would only solidify the omnipotence of the two-strokes as the bikes became ever more powerful and easier to ride. While manufacturers like Husqvarna and ATK continued to offer high performance thumpers for the well-healed vet rider, the motocross main stream was two-smoke all the way.

Stone Axe: The YZ250F was a remarkable machine for more reasons than just its impressive performance. Perhaps most important of all was its remarkable reliability. As Honda, Kawasaki and Suzuki would find out three years later with their first 250F attempts, it was not easy to develop a highly stressed, high-rpm motor that is both fast and reliable. If the original YZF had been as unreliable as the original RMZ/KXF, the whole 250F movement might have ended up DOA.

All that changed in 1998, with the introduction ofYoshiharu Nakayama’s pet project, the YZ400F. In the mid-nineties, Yamaha engineer Yoshiharu Nakayama had the ingenious idea to make use of Yamaha’s extensive road racing technology to help develop an all-new motocross machine. His idea was to take one of Yamaha’s successful YFZ road race motors, shrink it down to one cylinder, and then cram that into an YZ250 chassis. The result of this inspired bit of engineering was Yamaha’s 1998 YZ400F.

Smooth as silk: The original YZ250F mill in 2001 was a far cry from the 43hp monsters we see today. Pumping out just over 30 horsepower, the original YZF was actually less powerful than the best 125’s of the day. Where it did have an advantage was in the torque department, where it produced double the twist of most 125’s and did it over a broader range.

While the ’98 YZF was certainly a revolutionary machine, it was far from a fatal blow to the two-stroke. Like most of its valve-and-cam forebears, the 400F was big, heavy and a bit of an acquired taste. It required a complicated starting drill to get going and a deliberate riding technique to use properly. Power was smooth and torquey, but slower to build and less responsive than the two-stroke. There was also a great deal of compression braking to adjust to and a nasty bog if the throttle was applied too suddenly. For those looking for a modern alterative to the outdated 500cc two-strokes, the YZ400F was a gift from heaven. If, however, you were looking for a better KX250, the big blue thumper was no magic bullet.

In the fall of 2000, Yamaha flew YOT rider Ernesto Fonseca to Japan to debut their new YZ250F. Fonseca’s trip was a successful one, with a dominating victory on the new machine.

By the summer of 2000, the jury was still out on the two-stroke vs. four-stroke debate. The AMA was still allowing absurdly large 500cc plus thumpers in the 250 class, but aside from Doug Henry’s remarkable ’98 250 Outdoor title, the two-strokes still reigned supreme. Henry’s shocking Las Vegas victory on the prototype YZM thumper remained the four-stroke’s only win indoors and none of the other Big Four had followed Yamaha down the thumper path. There was no doubt, the YZ400F and its new brawnier brother the 426F, were potent motocross weapons. They were awesome Open class machines in every sense of the word, but in a world dominated by lightweight 125’s and 250’s, they were still a bit of an outlier. For the four-stroke to really go mainstream, someone would need to find a way to beat the lightweight two-strokes at their own game.

Achilles Heal: The only true chink in the armor of Yamaha new wonder boy was its ludicrously complicated starting drill.  Unlike today’s kick-and-go machines, it was necessary to find top-dead-center, nudge just past it, engage the compression release (pictured above the clutch), and give it a good swift kick. All the while being careful not to give it any gas (as you would have on every other two-stroke bike you had ridden up to that point). If it was hot, you had to first reach down to the carburetor and engage the hot start before beginning the starting the drill. Oh yeah, and if it was still in gear or flooded-forgetaboutit.

When Nakayama had come up with the idea for the original YZ400F, in the back of his mind he had also envisioned a smaller, lighter alternative. In the world of four-strokes, 250’s had always made great play bikes, but poor race machines. They offered just enough power to actually be fun (but not enough to be fast) and were light enough to not feel like a tank. Nakayama’s idea would be to keep the excellent handling and fun character of a typical 250 four-stroke, but inject it with a dose of high-rpm horsepower straight from the YZ400F.

In 2001, Yamaha had a good time poking fun at the controversy over the contested Presidential election. No word on whether DR. D got to build a track on the West lawn.

To accomplish the goal of building the world’s first truly competitive high-performance 250 thumper, Nakayama would rely on the groundwork laid by the YZ400F. It would use the same basic five-valve Genesis head design and super short stroke layout as the 400 and 426, but downsize everything for maximum weight savings. To maximize rpm and minimize friction, a 37.7mm slipper piston was employed on the 249cc mill. For the head, super hard and light titanium valves we employed to aid durability and allow the new bike’s stratospheric 13,500 rpm rev ceiling. To keep things as light and compact as possible, Yamaha spec’d the clutch off the YZ125, but deleted one of the 125’s gears, making the new bike a five-speed.

In 2001, this was the most high tech motor in motocross. The 249cc short-stroke mill featured five (titanium) valves, a road-race inspired slipper piston, a ceramic-composite coated cylinder, magnesium cases, a 37mm FCR Keihin carb with throttle position sensor and a ear-splitting 13,500 rpm redline.

In 2001, the first rider to win a National on Yamaha’s new thumper was not a high-paid factory super star, it was actually journeyman racer Larry “Big Bird” Ward. Ward would take the victory at the Red Bud event, while riding for the Moto XXX privateer team.

At the time of the 250F’s launch, conventional wisdom held that for a four-stroke to be competitive, it needed major cubic inches. It was generally held, that anything less than a 400 had no chance of hanging with a powerful and lightweight two-stroke. With the introduction of the new YZ250F, this long held maxim was being put to the test. Yamaha’s new mini-thumper would compete not with 250cc two-strokes (where its 426F big brother was allowed to play), but with 125cc two-strokes. This was due to the AMA’s odd displacement rule that allowed four-strokes up to 249cc in the tiddler class (in fairness, this misguided rule probably had XR250’s in mind, not 14,000 rpm rev-rockets). Still, the question remained- could a 250cc four-stroke truly be competitive in the most hotly contested class in motocross?

In 2000, I put a deposit down on a YZ250F the first day it was announced to the press. Nearly eight months later, I had the first one to make its way to my dealer. It was quite a change after getting off my YZ400F, but a really fun bike to ride and race. My only beef with it was its occasional refusal to start for no apparent reason. If any bike ever needed an electric starter, this one was it.

While the new YZ250F was designed to be raced in the 125 class, most of the machine was actually based off its 250cc two-stroke sibling. The YZF used suspension right off the latest YZ250 and shared the same basic geometry with the smoker. Although its motor was slightly larger overall, it actually weighed one pound less than the two-stroke YZ250 mill. At 225 pounds, the YZ250F was around the same weight as a 250 two-stroke of the time, but significantly heavier than the 125’s it would be competing against.

Parts bin: The forks on the YZF were stolen right off Yamaha’s own YZ250 two-stroke. They were identical, with the exception of slightly more compression damping to compensate for the bikes more pronounced compression braking. In 2001, these were some of the best forks in the 125 (or 250) class.

In terms of performance, the 2001 YZF’s main advantage was in the torque department. Compared to a 125 of the time, the original Yamaha 250F actually made less horsepower than a 125 of the day. At just over 30 horsepower, the YZF was no match for a 250 two-stroke and as much as five horsepower behind the powerhouse KTM 125. Where it had an advantage, was in the breadth if its power. The YZF started making its power far sooner than any 125 and kept making that power long after the ring-dings gave up the ghost. With a redline of 13,500 rpm, the YZF could do in one gear what would take three shifts on a 125.

A unique feature of Yamaha four-strokes of the time was this five-valve Genesis head. Employing five titanium valves (three intake, two exhaust), the Genesis design allowed the maximum flow from the minimum surface area. Originally debuted on Yamaha’s 1984 FZ750 sport bike, the Genesis head was a staple of Yamaha four-strokes for more than two decades.

Off the line, the YZF felt about like any other 250 four-stroke. Low-end power was roughly the same as a XR250R or KLX300. This was far better than a CR125R, but a far cry from the massive blast of power delivered by an YZ426F. Once into the midrange, the YZ250F delivered a pleasant spread of ponies on the way to its ear-splitting top-end shriek. At no point in the curve did the YZF hit or explode, it just revved and revved and revved. Getting the 250F to hook up was incredibly easy and it could find traction on surfaces that would leave 125’s spinning doughnuts.

To say the new YZ250F was a big story would be a major understatement. Yamaha’s little thumper made nearly every magazine cover for a time in the early 2000’s.

In terms of outright acceleration, the YZ125 and YZ250F was actually a virtual dead heat. Off the start, its smooth power and ease of use were not enough to outweigh its horsepower and weight disadvantage. On the track, however, where jumps are often right out of turns and loam transforms to baked clay in the summer sun, the 250F’s superior torque and traction were a huge advantage.

All was not perfect, however, with the new miracle thumper. In addition to its weight disadvantage, the YZ250F offered its own unique challenges. For starters (if you will pardon the pun) the YZ250F could be an absolute nightmare to get lit. There was no automatic decompression release and the bike was no kick-and-go affair. Even worse, sometimes the bike would start first kick, and other times it might take you twenty. If it was hot, you might as well get comfortable, because you were likely in for a wait. While the 426F was a well-known bear to start, the little 250F turned out to be even worse. Not good.

Ernesto Fonseca would enjoy quite an impressive inaugural season on the all-new Yamaha four-stroke. The Costa Rican native would dominate his way to the 2001 125 West Supercross title and finish an impressive third overall Outdoors.

There was also the matter of the YZF’s unique power characteristics to come to terms with. The compression braking on these early YZF’s was very pronounced and something most two-stroke riders were unaccustomed to. Shutting off too early into a corner was pretty annoying, but shutting off on the face of a jump could spell disaster with a massive endo. Another problem was perception, as riders buying the new 250F expecting a smaller 426F were in for a disappointment. It had none of the 426’s hard hit and massive grunt. To get the most out of the small thumper, you had to keep it pinned like a 125 and slam in the gears. As long as you thought of it as a torquey 125, you were golden. If you treated like a two-stroke 250 or big-bore thumper, however, you were in for frustration.

In the suspension department, the YZF offered some of the best performance on the track in 2001. When designing the YZ250F, Yamaha had had an excellent parts bin to pillage and they used that advantage to great effect. The suspension for the 250F was taken right off the class leading YZ250 and only needed few subtle tuning changes to get up to spec.  Because of the severe weight transitions caused by the motors compression braking and slightly different weight bias, the forks were set up with slightly more compression than on the YZ250. With this set up, the YZF owned the best forks in the class (along with its YZ125 stable mate). The suspension was plush over the rough stuff, while offering good big-hit absorption. As always, bigger (vet) or faster (pro) riders could have benefited from stiffer springs, but overall, the Yamaha’s Kayaba’s did an excellent job of taking the bite out of the track.

For the rear of the 250F, Yamaha once again raided the corporate parts bin. The YZF used the shock, swingarm and linkage straight off the YZ250 two stroke to great effect. It was well damped and capable of handling obstacles big and small with nary a whimper.

Just as in the front, Yamaha pilfered the rear suspension for the YZF straight off their YZ250. The shock, swingarm and linkage were all YZ250 pieces. This gave the YZF a great advantage right out of the box, because the YZ250 two-stroke was considered by most to have the best rear suspension on the track. The YZF tracked straight and true through the whoops and gobbled up any bumps thrown into its path. It was smooth on breaking bumps and actually better than its two-stroke stalemate on choppy tracks due to the thumpers tractable power delivery. This was one well-sorted rear end.

In 2001, this 250mm front stopper was one of the best in motocross. When you combined its power with the built in braking provided by the motor, it was easy to go in deep on the YZ250F.

Handling on the YZF was another area where the power of the motor gave it a different character than the bikes it competed against. At nearly 230 pounds ready to ride, the YZF weighted nearly twenty pounds more than a typical 125. This meant the 250F was not quite as nimble in quick transitions and required more work to muscle around. In deep sand and through really deep whoops, the extra weight could be felt and the 250F was more difficult to get “on top” of obstacles. In the air, the YZF flew straight and true, but was more difficult to whip or change direction on than a featherweight 125.

After the run away success of the YZ250F, it would not take long for the other Big Four manufacturers to jump on the 250F bandwagon. By 2004, the 125 two-stroke would be an endangered species in the Outdoor Motocross Nationals.

Where the YZF had an advantage, was in off-cambers and low traction situations. Due to the compression braking of the motor and its more forward mounted weight bias, the 250F offered front wheel traction never dreamed of on a 125. It could be leaned into bends at angles that no two-stroke rider could even consider. In off-cambers and on slick dirt, the YZF clung like it was riding on flypaper compared to a pipey 125 two-stroke. If there was a jump right out of a turn, the four-stroke had a massive advantage with its superior traction and torque. It was not better in every situation, but when combined with its power advantage, the 250F was hard to beat.

The cheater: In 2001, Yamaha created a bike that took advantage of a rule no one expected to be exploited. Two-fifty thumpers were great play bikes, but too slow to be anything but toys. Then along came the YZ250F, and it re-wrote everyone’s expectations of what a small four-stroke could do. It was fast, easy-to-ride, and maybe most importantly, reliable. Fair or not, one thing is for sure, cheating was never more fun.

With the introduction of the 2001 Yamaha YZ250F, the writing was on the wall for the future of the two-stroke 125. Because of some misguided rule making and a lack of foresight, the AMA allowed the thumpers to have double the displacement in the 125 class. With this rule, the 250F was given an advantage no 125 could overcome. If the limit had been 175cc or 200cc, the outcome would probably have been different. As it was, however, Yamaha took advantage of the loophole and changed the face of the sport forever. For better or worse, we live in a four-stroke world, and that fate was sealed by the 2001 Yamaha YZ250F.