• Modified the rigidity of the frame and swingarm to improve handling and reduce weight
• Decreased the combustion chamber from 21.5 to 21cc
• Reshaped cylinder exhaust ports and raised them 0.4mm higher
• Increased crankshaft taper from 17 to 18mm and the nut size from 10 to 12mm to improve rigidity and reliability
• Made second gear slightly taller. The ’02 version was 25/16 or 1:1.563, whereas the ’03 version is 23/15 or 1:1.533
• Re-valved front and rear suspension
• Re-designed rear brake caliper and integrated the master cylinder for weight reduction. Piston diameter has been decreased from 12.7 to 11.6mm–saving 45 grams
• Increased rear brake caliper piston diameter from 24.5 to 27mm to make it 20 percent more rigid and improve braking characteristics
• Fuel tank is 350 grams lighter
• Revised piston material and shape in the front brake caliperWHAT EFFECT WILL THE YZ450F HAVE ON YZ250 SALES?
The new quarter-liter motocrosser will probably have very little effect on YZ450F sales. Most people who will buy four-strokes are already four-stroke owners and will simply replace old equipment when the new YZ-F makes its debut. Although both machines can get you around a racetrack in a hurry, the buying public seems to be divided when it comes to taste. There are very few people sitting on the fence, who haven’t already made the change, but as four-stroke technology continues to reinvent itself at an accelerated pace, there will still be people who will explore their options more thoroughly before making a buying decision.HOW IS THE YZ250 MOTOR?
Downright killer! The engine is the highlight of the new YZ250, and it works about everywhere you would want it to. It features great off-idle response, coupled with big power throughout the midrange and top-end. Delivery is crisp and clean, and is more usable than on the ’02 version. We also liked the taller second gear, which is arguably the most important gear in a transmission. We know power can still be improved by the aftermarket through cylinder porting, head mods and a performance exhaust, but it will be more difficult to get the type of gains people have come to expect. Every tester jumped off the YZ and said it was race-ready in stock form. It also makes us wonder just how much more power the manufacturers will be able to squeeze out of 250cc two-strokes in the future.WHAT JETTING WORKS BEST?
The 38mm Keihin PWK carburetor with a Power Jet and throttle-position sensor is set up really well for sea level. We tested during the early summer months when it was 80-95 degrees with minimal humidity and the 178 main, 200 main air and 50 pilot worked well with the clip in the third position from the top.
HOW IS THE CHASSIS?Overall feel of the frame seems a little improved over last year. We didn’t notice it much in ’02, but the new chassis feels as though it flexes less and steers better. Everything just feels a little more precise, yet at the same time it seems a bit more forgiving. It’s really noticeable when entering a section of deep braking bumps or when attempting to blitz a section of whoops.HOW IS THE SUSPENSION?
Fork and shock action are improved, but we still think there is plenty of room to make it even better. When you compare factory motors and factory suspension to production hardware, there is a bigger gap between the suspension Jeremy McGrath and David Vuillemin use for racing and the stuff you buy. Production motors, on the other hand, are pretty good, especially when the aftermarket has performed its magic. We know everyone can produce plusher and more forgivable suspension, but all companies seem to be in the profit-taking mode and don’t believe the consumer is willing to fork out the extra cash.
To Yamaha’s credit, the R&D team has done a good job with improving upon the Kayaba components. Although the fork seems to be a little harsh during the initial and middle portion of the stroke, it is better than last year’s. The same with the shock, which could be the result of new valving specs or increased chassis rigidity. Either way, Yamaha is making improvements, but we think this might be one of the YZ250′s weaknesses when shootout time rolls around in the next month or so.HOW ARE THE BRAKES?Every year Yamaha continues to get closer to Honda’s legendary binders. Power and feel are similar to the CR250R’s, but the YZ’s do feel a little grabbier.
WHAT’S NEXT FROM YAMAHA?Most likely the next big thing will be a 125cc liquid-cooled four-stroke motocrosser to compete against 85cc two-strokes. We also expect Yamaha to make a dual-sport version of the WR450F to compete against Suzuki’s street-legal DR-Z400S.Word has it Yamaha is working on a new mini motocrosser, but there are conflicting stories as to the exact size. Some insist it will be a 50cc two-stroke with suspension and liquid-cooling, while others say it will be a YZ65 two-stroke.
I grew up racing Yamaha YZ250s in the CMC Golden State Nationals and Trans-Cal events, but I haven’t always been that fond of them, especially in the mid-’90s. But during the last few years they have grown on me once again. The improvements to the ’03 model, however subtle, are noticeable and the bike is definitely better than last year’s version. Midrange power is stronger and it pulls longer on top. This makes it easy to stretch out gears and rev out the engine on jump faces that might otherwise require a sketchy last-second upshift. Handling also feels better in the area of stability; however, I still don’t consider the suspension plush in any sense of the word. I seem to get a lot of feedback from the fork on small and midsize bumps that I don’t get from some of the other quarter-liter two-strokes. So would I recommend the YZ250? Absolutely! Although we won’t know for another two months how it stacks up against all the other machines in our shootout, it’s a great all-around package. Perhaps the bigger question should be: How will the YZ250 compare to the YZ450F–and should you wait to get one of those? Well, I’m cautiously optimistic that Yamaha did its homework and will beat the benchmark set last year by Honda’s CRF450R. Who knows, the YZ450F might turn out to be so good that it continues to pull people into the world of four-stroke motocrossers. But for the type of riding I do, I still haven’t found one perfect do-it-all bike from any manufacturer.–Ken Faught/5’10″/203 lb/Vet Intermediate
The best way to describe the ’03 YZ250 is responsive. The new motor feels like Yamaha has pulled Jeremy McGrath’s engine out of his race bike and transplanted it into the production model. I know that’s an exaggeration, but the motor is that good! Power stays strong from idle all the way into the upper-rpm range. The YZ is very nimble and has the ability to seek out a wide variety of lines with little work. Suspension is slightly harsh in the mid-stroke coming into deep braking bumps, but that is about my only complaint. Besides that, the fork and shock work really well everywhere else. This is a great all-around package with an outstanding motor.–Jason Webb/5’10″/175 lb/Intermediate
The YZ250 gets me excited just thinking about it! It is the most fun 250 two-stroke I have ridden to date. This bike does everything well and then some. The motor is so good! Bottom comes on real smooth but it gets the power to the ground in a hurry. On hard, slippery surfaces–such as Saddleback in the afternoon–the YZ doesn’t slide around or do anything unpredictable. Midrange power is so wide it will suit most any caliber rider. But hang on when you hit the straights because this bike will tear your arms right out of their sockets. If there is a flaw in the 250, it is its shock. The shock has a little kick to it when coming out of choppy, rutted corners. I even set the sag a little lower than usual and it still wanted to hop just a bit. With a little more testing and refining, I know we can get it to work really well. I know this because I have an ’02 that did the same thing, and a little revalve worked wonders. The chassis is stable and the 250 corners like a dream. It is hard to buy a stock bike and leave it for the whole year but the YZ250 is an exception to that rule. Throw a good aftermarket bar on it and you will thank me later.–Kris Keefer/5’11″/165 lb/Pro DR