In 2014, Yamaha introduced an impressive quarter-liter motocross model with the all-new YZ250F. The all-new bike incorporated much of the technology found on the YZ450F, providing the YZ250F with the same fuel-injected, rearward-inclined engine that allowed Yamaha engineers to produce more power than ever in a 250 and thereby putting it atop the class. The 2014 model also featured an all-new bi-lateral beam aluminum chassis that helped propel the YZ250F in the departments of handling and ergonomics.

After such a radical redesign last year, Yamaha’s 2015 YZ250F came to the table with only a few updates to evolve the bike and polish its recent improvements. Yamaha invited us out to the famous Southern California track Glen Helen Raceway to ride the bike. We happily obliged.

Although we really liked the 2014 YZ250F, the one complaint we had was its finicky starting when the motor was already warm. The motor features an excellent fuel-injection system that uses a single 10-hole fed by a fuel pump delivering 47 psi to its 44mm Keihin throttle body. But if the engine dies after a tip-over, trying to restart it was quite a chore – and it’ll likely require at least four attempts to kickstart it back to life. Yamaha engineers addressed the issue on the 2015 using 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 change clearly makes a difference and makes the 2015 much easier to quickly kick back to life.

Yamaha also updated the 2015 YZ250F’s ECU, providing an immediately noticeable improvement from the first hit of the throttle. Yamaha engineers recalibrated the mapping for the 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. Yamaha notes the updated maps gives the 250F broader midrange torque and smoother high-rpm overrev, but we didn’t really notice much difference because the engine is already potent. The 250F’s bottom-end throttle response has eliminated some of the off-idle chop of the 2014, however, and it’s so good that you can practically feel each revolution build as you roll on the throttle. Although some of the testers even felt it made more power down low, we know that it’s not any more powerful but just cleaner off the bottom.

Although the 77.0×53.6mm bore and stroke of the 250F’s motor are the same as the 2014, the 2015 piston’s ring lands have been changed for better oil retention. Yamaha also says 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, which we’ll eventually test firsthand on the dyno since we’re hanging on to our test bike for a bit. Whether true or not really doesn’t matter, since there’s no denying that the 250F is a rocket ship.

Our expert tester Ryan Abbatoye definitely sang the engine’s praises during testing, as it allowed him to clear a jump on the Glen Helen track that he had only been able to clear on a 450cc machine prior. He explained that the motor simply has no flat spots anywhere in the 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, but it’s also highly effective in delivering precise turning and providing stability on rough, high-speed straightaways. The slim ergonomic layout is also very comfortable with its very flat seat and a recessed fuel cap to allow the rider to seamlessly transfer weight forward when in the turns. Also aiding is a mid-ship fuel tank placement that provides an ideal center of gravity for the bike. The handlebar mount offers four different positions of adjustment for a total of 36mm of range.

Yamaha says it included a lighter throttle return spring to help reduce throttle pull effort by 20 percent. A small but notable change is where Yamaha replaced 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.

The 2015 YZ250F does get BNGs (Bold New Graphics) that are thoughtfully embedded into the radiator shrouds to make them less prone to peeling. The YZ250F will be available in two color schemes of 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 new black Excel rims.

Although Yamaha entered 2015 without need of change, Yamaha made enhancements without increasing the cost over the 2014 model. For 2015, Yamaha is keeping the 2015 YZ250F’s price at $7490. It’s not the least expensive bike in the class, but when you consider the technology and performance of the bike, it’s still a bargain in our eyes.

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 Specifications
MSRP: $7490
Engine: Liquid-cooled four-stroke single, DOHC four-valve head
Displacement: 249cc
Bore x stroke: 77.0 x 53.6mm
Horsepower: 40 rwhp (claimed)
Torque: N/A
Compression ratio: 13.5:1
Fuel System: Keihin EFI, 44m throttle body
Ignition: TCI
Transmission: Five-speed
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´
Trail: 118mm
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