2014 Yamaha Yz450f
Ignition
YAMAHA YZ450F
KTM 690 DUKE
MV ACUSTA F3 800
TROY BAYLISS
COLD-TIRE CRASHES
THE RIDE STARTS HERE
2014 YAMAHA YZ450F
CW FIRST RIDE
Essential elements of motocross
Jimmy Lewis
YAMAHA HAS BEEN turning motocross on its head ever since there was motocross, from monoshocks to modernera four-strokes. So installing the cylinder head backward on the radical 2010 YZ450F was not out of character. That machine met with mixed success, thanks to certain high-profile racers not getting along with it so well. But Yamaha stuck with the design and its masscentralization theme.
The all-new 2014 YZ carries on that theme, but nearly every part has been refined. The gas cap is concealed, since the whole tank—with increased capacity of 2.0 gallons—has been lowered and moved back in the frame. That allowed the airbox to grow a massive 256 percent on the dirty side of the air filter, which itself is now
35-percent larger and much easier to service. The formerly spiraling header of the rear-exiting exhaust has been replaced with a pipe that gets a tour around the front of the cylinder to gain the necessary tuned length, which allows the muffler to be nearly seven inches closer to the bike’s center.
The aluminum frame's headset has been moved 10mm to the rear, and tuned to give a more flex-free ride. Ditto the suspension, tuned to use less stroke while keeping the same bump compliance. The taper of the outer fork tubes makes them stiffer, and a multi-position-adjustable upper clamp holds rubber-mount handlebar clamps designed to keep that stiffness from jarring the rider, while providing enhanced control.
On the track, the YZ-F is still a front-wheel-steering machine that goes where you point it. Though it’s stiffer overall, the plushness the YZ-F was known for is still there. Having the right sag is key in setup (105mm is recommended, or a bit more for additional stability).
Huge changes in the engine also focus on greater mass centralization. Oil capacity has been decreased to one quart, now carried in a wet sump. Intake valves have grown one mm in diameter and cam timing is altered—all matched to new FI and dual-stage ignition mapping that’s gear-dependent. Overall, the engine is more compact and shorter, which allows the front frame rails to come closer together. Improvements to the transmission center on increased diameter of the shift-fork slider pins, which now slide on springs. A bearing aids shift-selector detent action.
Right away, we felt the bump not only in power but in torque throughout the spread. The bottomend is smoothed out and mellowed, but there’s improved throttle response everywhere: The bike revs quick and pulls hard all the way to the limiter.
Yamaha has definitely improved the YZ450F. No longer just a greatturning bike with plush suspension, the $8490 YZ is faster, easier to ride, better suspended and even more masscentralized. You can feel it.
YAMAHA
YZ250F
LITTLE LEANER
Yamaha’s 2014 YZ250F ($7490) is a smaller version of its 450cc big brother, replete with a rearwardleaning cylinder with intake in the front and exhaust in back. The 250F finally gets fuel injection, too. The engine has the same bore and stroke (77.0 x 53.6mm) as before, but its new twin-cam head has four titanium valves in place of five. A new chassis completes the package.
BY THE NUMBERS
399
CUBIC CENTIMETERS:
The displacement of the 1998 Yamaha YZ400F, which was followed by the YZ426F in 2000 and then the YZ450F in 2003.
2
NUMBER OF STEPS
now needed to access the underseat airfilter assembly. Two fewer than on the 2013 model.
0.4
GALLONS:The increase in fuel capacity of the 2014 YZ450F compared to the 2013 model.
