2012 Yamaha YZ450F | Dirt

Still Exotic

When Yamaha dropped the reverse-top-end bomb on the 450cc class in 2010, the YZ450F was radical and readily embraced by professional racers. Thankfully, the all-new design has proven reliable for amateur riders, too. It runs hard and stays strong. After such a major redo, Yamaha is going with small-but-welcome changes for ’12. The changes are more extensive than in ’11, and aside from the addition of black rims and a gold chain, all are improvements the rider can feel.

Within the ECU are fueling and ignition adjustments that smooth power delivery and make the roll-on friendlier. The difference between the previous-generation’09 engine and the ’10 was huge; it went from having smooth power to being snappy and zappy. The muffler is now 42mm longer to satisfy AMA Pro Racing sound regulations and tame the snort off the bottom. The YZ still has a light flywheel feel and spins up fiercely, but the ponies get to the ground with less drama than you would expect from an engine that revs so quickly. This engine and transmission combo is strong off the starting gate as well. Clutch engagement is smooth and the lever feels fairly light. Since the air intake is right in front of you, induction noise is especially noticeable, and getting to the air filter is a bit of a chore. But on the plus side the filter stays clean longer since it’s not sucking roost off the rear tire, and with the header pipe safely tucked away between the frame spars you don’t have to worry about denting it.

Further invisible-but-welcome changes occurred inside the Kayaba suspension. Damping rates were altered to combat brake dive in the fork and the shock benefits from fine-tuned rebound and additional high-speed compression damping.

And where the rubber meets the dirt, the latest Dunlop Geomax MX51 intermediate tires replace the phased-out D742FA front and D756 rear knobbies. Wheel control is good, and the bike feels right in the zone, dancing between nimble and stable. The purpose of the “backwards” engine was to centralize mass and reduce rider effort in transitions, and that concept works even better now that the suspension has been improved. When the bike was new in ’10 there was a tendency to forgive details like the intake honk and the width of the bike between the rider’s knees while seated. Now that the “new” has rubbed off, we’d like to see some improvement in these areas.

Regardless, the Yamaha remains a serious contender. It can handle the rigors of world-class motocross and supercross competition, yet also earned the 2011 Over-30 and Over-40 Vet World Motocross Championships. That is a wider range of capabilities than we ever felt this narrowly focused MX bike could possess. The important parts of the picture are there. With just a few key changes, the YZ450F remains a techno-marvel and a damn fine dirtbike.

2012 YAMAHA YZ250F
Not Backwards Yet

This year’s YZ250F has more updates and new parts than its big brother, but it doesn’t have a backwards cylinder yet, and it’s still sucking its fuel through a carburetor. That mechanical mixer is now 2mm larger at 39mm, and inhales through a less restrictive filter cage. Inside, the piston and pin have been lightened by nearly 10 percent for even quicker acceleration. The engine is held in a new Bilateral Beam frame like that of the YZ450F, and the fork offset has been changed to increase trail and thus stability. Fork tubes and triple clamps are now burlier to offer increased front-end rigidity, while internals have been changed front and rear to compliment the new frame’s rigidity. With the new frame and revised suspension, the already fine-handling YZ250F works even better. It balances stability and responsive handling in a nice package.

Though the engine looks like the same old thing, on-track it has traded some of the traditional Yamaha torque for better lungs when the revs spin up. There is no doubt that mid to top-end performance is well up, and now better suited to pilots who love to twist the grip hard. If the carburetor isn’t a deal-breaker—and it isn’t for us — then the proven and reliably YZ250F remains a great choice in the 250cc class.

Tech Specs

The latest, greatest iteration of the YZ400F that started the four-stroke motocross revolution.
Honda CRF450R, Husqvarna TC449, Kawasaki KX450F, KTM 450 SX-F, Suzuki RM-Z450.

Price $8350
Engine type l-c single
Valve train DOHC, 4v
Displacement 449cc
Bore x stroke 97.0 x 60.8mm
Compression 12.5:1
Fuel system EFI
Clutch Wet, multi-plate
Transmission 5-speed
Claimed horsepower na
Claimed torque na
Frame Aluminum twin-spar
Front suspension Kayaba 48mm fork with adjustable compression and rebound damping
Rear suspension Kayaba shock with adjustable spring preload, high/low-speed compression and rebound damping
Front brake Nissin two-piston caliper, 250mm disc
Rear brake Nissin one-piston caliper, 245mm disc
Front tire 80/100-21 Dunlop Geomax MX51
Rear tire 120/80-19 Dunlop Geomax MX51
Rake/trail na
Seat height 39.3 in.
Wheelbase 58.7 in.
Fuel capacity 1.6 gal.
Claimed curb weight 245 lbs.
Colors Blue/white, white/red
Available Now
Warranty na
Contact Yamaha Motor Corp. USA 6555 Katella Ave. Cypress, CA 90630 800.962.7926 www.yamaha-motor.com

VERDICT: 4 out of 5 stars.

Radically different and high-tech, yet friendly enough for the average rider.

They say: "It stands apart in the motocross scene."
We say: "Not as new as it once was, but still as good as ever."
Get your head on straight! The YZ’s cylinder slants rearward to help centralize mass, and puts its intake up front and exhaust in the rear.