After dominating the class as an all-new model last year, the 2015 Yamaha YZ250F arrives with minor tweaks that yield major improvements. Will it be enough to keep the Blu Cru on top?
After years of having a solid but not quite top-line contender in the 250cc motocross class, Yamaha came out swinging in 2014 and knocked the quarter-liter contingent on its rump with an all-new YZ250F. Replicating the technology incorporated in its radical YZ450F, the YZ250F’s fuel-injected, rearward-inclined engine broke new ground in the class, and its new cylinder head’s symmetrical port design allowed Yamaha engineers to make more power than ever. At the same time, an all-new bi-lateral beam aluminum chassis set new standards for the YZ250F’s handling and ergonomics.
The 2014 YZ250F dominated the class, recording the lion’s share of shootout wins and Bike of the Year honors around the world, and this year the YZ250F is proving its mettle in AMA National competition, with multiple wins by factory-backed Yamaha riders Jeremy Martin and Cooper Webb in the 2015 Lucas Oil 250cc Pro Motocross Championship.
With so much work invested in last year’s model, Yamaha’s approach with the 2015 YZ250F was simply to evolve the design by addressing a few minor issues to polish the machine. When Yamaha invited us out to Southern California’s Glen Helen Raceway to try it out for ourselves, we jumped at the chance. Last year’s YZ250F was awesome. This year, it’s even better.
One thing that we absolutely didn’t like about the 2014 YZ250F was how finicky the bike could be to start up when warm. It’s blessed with an excellent fuel-injection system, which uses a single 10-hole fed by a fuel pump delivering 47 psi to its 44mm Keihin throttle body, and that helps it to rip up any motocross track all the more effectively. But kill the engine after a tip-over, and you could expect to give it at least four heavy boots to the kickstarter before it would fire up again. For 2015, Yamaha engineers have addressed the issue by going to a new exhaust cam that retains the lift and duration of the previous cam but the angle of the auto decompression pin has been altered 6 degrees. The difference is obvious, as the 2015 is way easier to kickstart, firing up much more readily than the 2014 model.
Another change for 2015 involves the YZ250F’s ECU, and it, too, is immediately noticeable right from the first hit of the throttle. Yamaha engineers have recalibrated the system’s 3D fuel and ignition maps, which are still adjusted based upon gear position. The new maps offer smoother power control at the first hit of the throttle. While Yamaha claims that the maps also give the 250F a broader mid-range torque and smoother high-rpm overrev, we honestly didn’t notice because the engine is already potent. What we can say is that the 250F’s bottom-end throttle response has eliminated some of the off-idle chop of the 2014. It’s so good that you can practically feel each revolution build as you roll-on the throttle. It’s such a difference that some members of other test crews swore that the YZ250F was making more bottom-end power than last year’s bike. It doesn’t. It’s just cleaner down low.
Internally, the YZ250F’s engine also gets a few minor tweaks for 2015. Its 77.0×53.6mm bore and stroke are the same as the 2014—and the 2013 for that matter—but the 2015 piston’s ring lands have been changed for better oil retention, and the titanium exhaust valves have a new coating that is more durable than the previous coating. The five-speed transmission’s gear ratios are unchanged for 2015, but the gear stop lever has been changed from a ball-bearing-style to a positive roller-style to improve shift quality. The 250F’s power is still transmitted through a beefy nine-plate clutch.
Yamaha has claimed all along that the YZ250F engine makes 40 horsepower, and since they let us keep the unit we sampled at Glen Helen, we intend to put that claim to the test on the dyno. Whether that claim will prove to be true or not really doesn’t matter, since there’s no denying that the 250F is a rocket ship, building fantastic thrust right off the bottom and transitioning into a healthy mid-range and maintaining its hard pull all the way to the rev limiter.
After spending all morning on the Glen Helen track, expert tester Ryan Abbatoye reaffirmed his admiration for the engine, which even delivered enough drive to allow him to clear a jump on the Glen Helen track that he had previously only been able to clear on a 450cc machine. The easiest way to explain it as that there are simply no flat spots anywhere in the YZ250F’s powerband. Experts will love it because it is fast, but novice and vet riders should enjoy its smooth, controllable power character as well.
Glen Helen was open for practice by the public when we tested the YZ250F, so it didn’t take long before the track was extremely rutted up by the constant pounding of knobby tires. That was actually a good thing, as it gave us a chance to gauge the new front fork settings that Yamaha has come up with for the YZ250F’s KYB Speed-Sensitive System inverted front fork. The 2015 has been set up with slightly more oil than the 2014, and its compression and rebound settings are firmer than the 2014’s. The choppy Glen Helen track convinced us to reduce the rear sag height and also decrease the compression damping to bring the suspension into balance. After that, we had no complaints with the action of the fork or its fully adjustable KYB rear shock, which could tame all of the gnarly ruts and bumps on the track.
The YZ250F’s aluminum bilateral beam chassis isn’t only pretty to look at, it’s also highly effective, delivering precise turning manners while remaining arrow stable on rough, high-speed straightaways. It’s also comfortable, thanks to a slim ergonomic layout that features a very flat seat and a recessed fuel cap to allow the rider to seamlessly transfer weight forward when in the turns (the YZF’s 2.0-gallon fuel tank is located mid-ship in the chassis, under the seat, in keeping with its mass-centralization goals). Adding to its adjustability is a handlebar mount that offers four positions for a total of 36mm of range to accommodate riders of various sizes.
Yamaha has incorporated other refinements that either aren’t as readily apparent on the track, or they are mostly cosmetic, but they are still worth noting. They include a lighter throttle return spring that is claimed to reduce throttle pull effort by 20 percent. Another nice change is the replacement of the three 8mm bolts that hold the upper “fuel tank” shroud with Dzus fasteners for completely tool-less removal when servicing the YZ250F’s air filter.
The 2015 YZ250F wears the same 250mm wave rotor front disc and two-piston caliper as the 2014 model. While that is a little bit of surprise since the competition is making the move to an even larger 270mm front rotor, we can’t gripe about the Yamaha’s front braking power or feel, and the same goes for the 245mm rear rotor and single-piston caliper out back.
Of course, the 2015 YZ250F gets new graphics that are embedded into the radiator shrouds to make them less prone to peeling, so if you like them, they should stick around for a while. The YZ250F remains the only 250cc motocrosser available in two color schemes as well: Team Yamaha Blue/White, or a Euro-inspired White, Red and Black. Capping off the styling appointments in either color are a new Gold D.I.D. 520 chain with a coating that makes it more corrosion resistant and black Excel rims, also new.
But this might be the best part: All the changes Yamaha has made to enhance the 2015YZ250F don’t come at additional cost over the 2014 model. Yamaha is holding the 2015 YZ250F’s price firm at $7490. That’s a lot of money, but when you consider the technology and performance that Yamaha has poured into the YZ250F over the past two years, it’s still a bargain.
The 2014 Yamaha YZ250F was truly revolutionary. The 2015 builds upon that foundation. We say that Yamaha’s Japanese and European rivals had better have their noses to the grindstone if they hope to topple the amazing 250cc motocrosser from its position at the head of the class.
2015 Yamaha YZ250F
Engine: Liquid-cooled four-stroke single, DOHC four-valve head
Bore x stroke: 77.0 x 53.6mm
Horsepower: 40 rwhp (claimed)
Compression ratio: 13.5:1
Fuel System: Keihin EFI, 44m throttle body
Final drive: Chain
Frame type: Bilateral beam aluminum
Front suspension: Inverted KYB fully adj. fork w/Speed Sensitive System; 12.2 in. of travel
Rear suspension: KYB fully adjustable monoshock w/piggyback reservoir, 50mm piston; 12.4 in. of travel
Front brake: Nissin two-piston caliper 250mm wave-style disc
Rear brake: Nissin single-piston caliper 245mm wave-style disc
Front tire: Bridgestone M404-A 80/100-21
Rear tire: Bridgestone M403 100/90-19
Wheelbase: 58.1 in.
Rake: 27°, 08´
Seat height: 38.0 in.
Ground clearance: 12.8 in.
Wet Weight: 231 lbs. (claimed)
Fuel capacity: 2.0 gal.
Color choices: Blue & White / White Red & Black