Yamaha has billed its rearward-slanted cylinder as revolutionary to the motocross world since it’s introduction in 2010, but the results of the YZ450F in shootouts and racing didn’t quite reflect Yamaha’s sentiments. While the premier class racer got the all the technical love, the YZ250F seemed to be forgotten by Yamaha, going through revisions rather than a total makeover like its larger sibling. And that wasn’t an entirely bad thing. The chassis was one of the best in the class, but the
power output and use of a carburetor hampered the YZ250F’s efforts to be on the same level as the brutish KX250F and RM-Z250. We always just wanted more from the blue bike’s mill to fully utilize the fantastic chassis. Finally the quarter-liter racer gets the same backwards configuration and fuel injection, and right up front we have to say, “Viva la revolution!”
Earlier this year MotoUSA sampled a pre-production YZ250F in the 2014 Yamaha YZ250F Quick Ride article, and we were left impressed. We did, however, wonder if the production version would be, as Yamaha had assured us, on the same level. In order to prove the YZ you can buy at the local dealership would be just as potent, they shipped us off to Monster Mountain in Alabama for a second ride.
Yamaha’s engineers explained that although the frame is all new the dimensions and angles are the same as the 2013 model. What did change was the center of gravity or, as it was called in the tech presentation, concentration of mass. With the rearward-slanted engine and the airbox where the fuel tank would usually be, the heavier parts such as the exhaust and tank could be moved inward and closer to the center of bike.
On the track it is immediately apparent that the concentration of mass is not just marketing hype. Handling is quick yet stable – a plus for when the track ruts-up and any miscue will put you on your head. The only issue was a slight nervousness coming into the corner as the bike reacted so quickly. Dropping the forks in the triple clamps to be flush with the caps settled the front-end down enough to allow us to charge hard into a rut or berm without worry. At the back three clicks of low-speed compression, a quarter-turn out on the high speed and two additional clicks of rebound damping had the YZ250F handling like a dream.
The YZ250F’s Kayaba Speed-Sensitive System forks are some of the best we’ve tested and we are pleased to see that Yamaha has opted to use them on the 2014 model. Initial plushness is excellent and bottoming resistance was adequate for both See’s 175 pounds as well as my 225-pound girth. At the rear the KYB shock gets a longer spring and the reservoir has been flipped to the left side of the bike to make room for the exhaust. After our initial set-up of the clickers, only spring preload was changed to suit our different weights. See at 102mm of sag while I set slightly more at 107mm.
“This bike felt really stable in the rough square-edged bumps and felt glued to the ground in those long ruts,” comments Chris See, our pro-level test rider. “With the minimal changes we made, I feel very confident on the YZ.”
The rider area is compact and allows the rider to move around easily, and See is happy with the bars in the stock location. I prefer the bars in the forward position to allow for more leverage on the front in the ruts. Either way, there are four handlebar locations to suit most riders. We both agree the bar bend was not the best, but that is some serious nit picking on our part. The airbox and radiator shroud area is slightly portly when first getting on the bike, but it wasn’t an issue on the track.
“The front area does feel wide,” says See. “But I do like that there is minimal side plastics to get your boots and knee braces caught on. I also think the bike looks really cool because it’s something so different.”
Handling and comfort are important pieces of the puzzle in the 250 class but the most crucial is the engine, and Yamaha has finally delivered. Tilting the cylinder to the rear of the bike 10.5 degrees not only moves the mass of the new four-valve head closer to the center of the bike, but also allows for straight and symmetrical ports for both the intake and exhaust. Additionally the intake is a true down draft design giving a straight shot of atomized fuel from the 10-hole injector in the 44mm Keihin throttle body. Combined with new camshaft profiles that have more lift and a lighter piston with less friction, Yamaha claims to have given the YZ250F more mid to high RPM torque and pulling power. Throttle response has also been improved.
From the first crack of the throttle it is clear that the 2014 YZ250F is a contender in the horsepower wars. Right off the bottom the power snaps to life and then pulls hard through the midrange all the way to the top-end. Gone is the boggy throttle response from the carbureted model of old. The new mill is so snappy we think taking a little off the bottom would make for a smoother exit out of the corner, but damn it is fun the way it is stock. Comparing the 2013 to the new machine is not apples and oranges, but firecrackers and M80’s. There just may be a new horsepower top dog on the block.
“The bike has a ripping motor from the bottom to the mid to the top,” exclaims See. “The 2014 is light-years better than the 2013. Also the bog is gone and that is a huge improvement to me.”
Yamaha also reworked the transmission with new shift forks on spring-loaded bars to reduce binding. The shift shaft diameter has also been increased from 12mm to 14mm, and a bearing has been added to the shift drum detent arm. The end result is solid and smooth shifts even under hard acceleration. Not once did we experience a false neutral or missed shift. The effort on the lever is light and feel on up- and down-shifts is precise.
The clutch basket received a needle bearing and the pressure plate rigidity has been increased 50 percent to match the engine’s elevated power output. The springs are also 20% stiffer. Second and third gears are now stronger to deal with the added power being fed through the clutch. Clutch feel is excellent and fade was not an issue even in the hands of See, who has been known to be a serial abuser of fiber and metal plates.
At the end of two days of riding at Monster Mountain, we have never seen such an improvement from one year to the next. Yamaha has absolutely revolutionized its 250-class offering, and we expect that some, if not all, of the 2014 YZ250F’s competition will be knocked down a peg or two by its excellent handling and killer motor.
Stay tuned for our upcoming 2014 250 Motocross Shootout to see how the YZ250F shakes up the rankings. The YZ250F is now a contender for the title without a doubt.