TransWorld Motocross Race Test: 2004 Yamaha YZ250F – Still the One?

By Donn Maeda

With all of the hype being centered around the new 250cc four-stroke offerings from Honda, Kawasaki and Suzuki, the 2004 Yamaha YZ250F has quietly begun to show up on dealership floors across the Nation without much fuss or fanfare. Though the bike has set the standard by which all others will be measured, don't think for a second that Yamaha engineers have sat back and rested on their laurels. Though the changes made to the '04 bike don't seem like much on paper, the new YZ250F from the Boys in Blue is back; better and badder for the New Year.


At the top of the short list of changes are the most important improvements. Internal engine modifications reduce pumping losses for increased midrange power. What the hell does this mean? Basically, the bottom of the piston skirt and the crankcases have been shaved away slightly to create a bigger opening for the crankcase pressure to escape through. The result is a freer-revving feel and improved throttle response in the middle of the powerband. These internal motor mods, coupled with revised carburetor settings and a new ignition curve, equal a lot more on the track than you might expect. But we'll get to that later…

Other changes include a titanium head pipe. The exhaust system maintains the same dimensions as last year's, but the addition of the titanium header helps contribute to an overall weight loss of a claimed two pounds. Things like lightweight brake pistons and titanium footpegs all add up. Like the rest of the Yamaha YZ line, the YZ250F comes equipped with a beefy set of 48mm Kayaba forks that boast all-new valve specifications.


On the track, the Yamaha YZ250F has the same solid feel that it has had since its inception, but something about the '04 is different. Gone is the overly-soft suspension performance and in its place is a nice, solid ride that is compliant, yet firm enough in stock condition for even heavier and faster riders. Last year, we got the forks to bottom severely, even with the compression clickers adjusted way in. The new fatter fork legs not only improve the YZ's overall ride, but they help the bike to handle more precisely in rough conditions. The added rigidity of the new front end is much appreciated in big braking bumps and ruts leading into corners, and our heavier riders really appreciated the way in which the fork handles slap-down landings. Both the front and rear suspension work extremely well in stock condition, and the components have a wide range of adjustability to suit riders of all sizes and speeds.

But what about the motor? Well, like we said earlier, the changes made to the motor actually produced more noticeable power gains than we had expected. The Yamaha YZ250F does, indeed, hit harder in the middle of the powerband, yet it maintains its awesome top-end overrev that we have come to love. Power down low is good, and roll-on throttle situations are predictable aboard the YZ250F. One thing about the YZ250F that stands out above the other new 250cc four-strokes is its mid-range hit. Like a two-stroke, the 250F packs an exciting punch that makes seat bouncing tricky obstacles not only easy and safe, but fun as well. In comparison to the other engines, the Yamaha has the least “traditional-four-stroke feel.” Is it faster than the new challengers? We'll have to wait for our official 250cc four-stroke shootout to draw that conclusion, but one thing is for sure: the YZ250F doesn't have much to worry about in the power department: this thing rips!

As delivered, our bike was jetted spot-on for our sea-level SoCal locale, and remained clean and crisp even when trying some aftermarket exhausts on the new bike. We were curious to see if existing '03 aftermarket exhausts would work well on the new, free-breathing '04, and were pumped to find that most of them pproduced the expected results. Among those that worked the best were the FMF, Bill's Pipes and Dr. D units.

As for the rest of the bike, the YZ250F is the same excellent bike it has always been. The brakes–front and rear–are superb, with great feel and power. The titanium footpegs don't feel any different under our feet, but they sure look trick! The new gripper seat cover is a nice addition, as it provides just the right amount of hind side traction.


The Yamaha YZ250F, in our opinion, is the best all-around motocross bike available. With five years of development and durability testing under its belt, the YZ250F has been a proven winner and a solid performer since it was introduced in '99, and the '04 version is definitely the best yet.



The 2004 Yamaha YZ250F engine underwent some efficient updates that result in big gains on the race track. The new powerplant packs a helluva mid-range punch, and still revs until the cows come home. To accommodate the higher speeds YZ250F riders will be attaining, the '04 bike received some much needed 48mm Kayaba forks. The new front end provides a much-improved ride and inspires plenty of confidence in rough conditions, g-outs and hard landings. Michael Young gets ready to re-enter the atmosphere on the TWMX test bike.


On the outside, the 2004 Yamaha YZ250F doesn't look a whole lot different than its predecessor, save for those trick titanium footpegs, the gripper seat cover and slightly altered graphics. The big changes, however, are hard to see, but easy to feel. Bigger forks and a beefier powerband will have '04 owners smiling inside their helmets.