It’s safe to say that Yamaha came about as close as a manufacturer can to setting the motocross world on fire with the YZ250F in 2014. Borrowing heavily from the architecture of its revolutionary YZ450F, the company’s all-new quarter-liter contender broke cover with a new, fuel-injected, rearward-inclined engine that places the straight downdraft intake out front and the exhaust in the rear. In addition to the new cylinder head’s symmetrical port design, which allowed Yamaha engineers to extract a lot more power from the engine, the compact engine allowed Yamaha to centralize the 250F’s mass in an all-new compact bi-lateral beam chassis that is shared with the YZ450F.
Still, savvy motoheads might beg the question that if all of the technology from the YZ250F was effectively handed down from its big sister, how is it that the 250F dominates its class where the 450F has pretty much failed to do so? There are a lot of ways to answer that question, and most of the debate would likely revolve around power management and, by extension, handling, when dealing with a high-steroid 450cc four-stroke single.
All we do know for sure is that the same radical changes that Yamaha brought to the YZ250F obsoleted the previous model and turned the new bike into a winner right out of the crate. The new design has already proven itself with multiple wins by factory-backed Yamaha riders Jeremy Martin and Cooper Webb in the 2015 Lucas Oil 250cc Pro Motocross Championship, where Martin is the current class points leader.
With a total revamp of the YZ250F already accomplished, Yamaha’s approach for 2015 was merely to improve on the existing design by addressing a few details – call it evolution of a revolution – and the company graciously invited us out to Southern California’s Glen Helen Raceway to sample the new machine for ourselves. We loved last year’s bike, but this year’s is even better.
If you read our review of the 2014 YZ250F in Alabama, you know that 2014 could be a cantankerous starter when hot, despite its excellent fuel-injection, which uses a single 10-hole injector fed by a fuel pump delivering 47 psi to its 44mm Keihin throttle body. 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 immediately noticeable, as the 2015 is way easier to kickstart, and fires up much more readily, than the 2014.
Once out on the track, another of Yamaha’s changes was immediately noticeable right from the first hit of the throttle: The 2015 YZ250F’s ECU has been recalibrated with new 3D fuel and ignition maps, which are still adjusted based upon gear position. The new maps provide smoother power control at lower rpm. Yamaha claims that they also offer broader mid-range torque and smoother high-rpm overrev, but those changes are less obvious. We can vouch for the 250F’s more linear throttle response off the bottom. The 2014 model felt somewhat choppy in the off-on throttle transition by comparison, but you can practically count each revolution build as you roll on the throttle now. It’s such a difference that some members of other test crews swore that the YZ250F felt like it made more bottom-end power than last year’s bike. Not so, says Yamaha. It just runs cleaner.
Internally, the YZ250F’s engine also gets a few minor tweaks for 2015. Its 77.0 x 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 change to provide better oil control, and the titanium exhaust valves feature a new coating that is more durable than the previous coating. The five-speed transmission’s gear ratios are unchanged, 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 transmitted through a nine-plate clutch.
And it’s a heck of a lot of power. Yamaha has claimed all along that the 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. But there’s no denying that this is one fast 250cc four-stroke, building fantastic thrust right off the bottom and transitioning into a healthy mid-range and maintaining its brawny feel all the way to the rev limiter. After spending all morning on the Glen Helen track, expert tester Ryan Abbatoye once again proclaimed his admiration for the engine, which delivered enough oomph for him to clear a jump he had previously only been able to clear on a 450cc machine. The biggest difference between the Yamaha and its competition right now is that there are simply no flat spots in the YZF’s powerband, which not only makes it feel fast but also makes it easier to ride by novice and vet riders.
As our riding session took place on an open track day at Glen Helen, it didn’t take long before the track was extremely rutted up by the constant pounding of the masses, and that 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 have been firmed up as well. Our experience on the choppy Glen Helen track led us to reduce the rear sag height and then reduce the compression to bring everything into better balance. After that, we had no complaints with the action of the fork or its fully adjustable KYB rear shock.
We loved the 2014’s slender, aluminum bilateral beam chassis, and the 2015 is identical in every way. It boasts razor-sharp turning manners while remaining straight as a string on rough, high-speed straightaways. Frankly, it’s excellent. Ditto for the YZF’s slim cockpit which features a very flat seat and a recessed fuel cap that allows the rider to really get forward on the machine 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). The handlebar mounts also offer four positions for a total of 36mm of adjustment to accommodate riders of various sizes.
Some of the other changes that Yamaha called out were either not readily apparent on the track, or they were mostly cosmetic, but they are still appreciated. They include a lighter throttle return spring that is claimed to reduce throttle pull effort by 20 percent. Maintaining the YZ250F’s air filter is now easier than before, as Yamaha has replaced the three 8mm bolts that hold the upper “fuel tank” shroud with Dzus fasteners for completely tool-less removal.
The 2015 features 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 have no complaints about the Yamaha’s front braking power or feel, and the same goes for the 245mm rear rotor and single-piston caliper out back.
Lastly, the 2015 YZ250F gets new graphics that are embedded into the radiator shrouds to make them less prone to peeling. The YZ250F remains available in two color schemes as well: Team Yamaha Blue/White, or White and Red. Capping off the styling appointments are a new Gold D.I.D. 520 chain with a coating that makes it more corrosion resistant and black Excel rims, also new.
Best of all, though, is that the changes Yamaha has made to enhance the YZ250F don’t come with an increased MSRP; Yamaha is holding firm with the YZ250F at $7490. That’s a lot of money, but when you consider the technology and performance that Yamaha has poured into the YZ250F, that’s chump change. Last year’s bike was revolutionary. This year’s is evolutionary. Either way, Yamaha’s Japanese and European rivals had better have done their homework if they are going to topple the YZ250F from its perch atop the 250cc motocross class.
|2015 Yamaha YZ250F Specs|
|Engine||Liquid-cooled four-stroke single, DOHC four-valve head|
|Bore x stroke||77.0 x 53.6mm|
|Horsepower||40 rwhp (claimed)|
|Fuel System||Keihin EFI, 44m throttle body|
|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|
|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|