2010 Yamaha YZ450F Review - Motorcycle.com

Alfonse Palaima
by Alfonse Palaima

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Last week, Yamaha introduced the radically-new 2010 YZ450F to the world at Maryland’s Budds Creek Motocross Park, and Motorcycle.com was there to see if its reversed engine layout and extreme mass-centralization was effective in giving the fresh YZ the agility it promises.

Mere miles from our nation’s capital, Budds Creek is draped across a small creek valley, giving the course its constant peaks and valleys – there’s not one flat turn or straight-away out there besides the holeshot line.

As MO’s resident lo-po tester – bringing you reviews of Piaggios instead of Ducatis – I was happy to get the opportunity to ride something with power enough to require holding on tight. But we all know, I’m not a track star, road or otherwise, so we brought along a new friend to MO, Joey Webb, to really put the new YZ to the test. Joey currently races the previous YZ450F and is fresh off testing Kawasaki's new KX450F, so it was going to be interesting to see how they compared.

Not quite a full Bubba-scrub, but far from Fonzie’s ride position on the track!

First things first, the new YZ is a clean-sheet full redesign of Yamaha’s largest sibling dirt bike, with only a rear brake cable as carry-over from the 2009 YZ. While the main difference between MY08 and MY09 YZs was a hydro-formed swingarm, this year almost everything is changed. The reversed engine configuration and addition of fuel-injection is matched by a new frame design and a ‘tornado’ vortex exhaust, all designed for mass centralization and a better handling bike for any rider.

As such, we’ve got some technology to catch up on. Kevin Duke’s unveiling report was only so delicious – you have to take a bite to get the full taste of this motocrosser. Joey did most of the laps while I packed the cameras full of photos and video clips, but I did manage to get a few licks in during our two-day test. Arm-pumped and primed, this is what we’ve learned about the 2010 Yamaha YZ450F.

Introducing the 2010 Yamaha YZ450F.

Centralize, Revolutionize, Revolve

Visually, the new YZ looks anorexic with slim flowing lines and less bodywork designed to show off the new bilateral-beam aluminum “double-S” frame. From the rear fender, over the relocated underseat gas tank and out over the 21-inch front wheel and 80/100-21-Dunlop D-742FA, the 2010 YZ is almost entirely new. It is aimed at being easier to ride and more controllable with better traction and a competitive edge. This especially holds true for the nearly 60% of you that actually ride these machines on the track.

Model year 2010 marks the time for a revolution in the Yamaha product lineup, gapping the 12 years since the first YZ-F was introduced in 1998. Since then, Yamaha admits to having only “evolved” the bike. “It’s time for an all-new YZ,” says Yamaha's press manager Tim Olsen.

First and foremost, there’s the slim and sleek look of the new YZ. It has flowing lines tip to tail, and engineered carb-less ‘gaps’ between engine, frame, saddle and sub-frame to make a very light-looking bike. Yamaha claims a total wet weight of 245 pounds, an increase of 7 pounds over last year’s model. Perhaps the stronger dual-beam frame is the culprit there.

It may not seem like much, but in a world of minute-yet-powerful changes, Yamaha is looking at the larger picture and trending forward into a new generation of motocross bikes with the 2010 YZ450F.

Turning around history

With a top-to-bottom redesign, Yamaha's new 450 is ready to rise to the top of the pack.

The YZ's reversed engine layout is human-like, with its breather facing forward and the exhaust porting to the rear. The 8.2-degree rearward cant of the 449cc powerplant is reminiscent of R. Crumb’s trucker cartoon, foot forward and making strides for the future.

Continuing the angularity and symmetry of the new design, even the cylinder is offset to the front of the crankshaft centerline. First seen in a few of the Yamaha scooters, the cylinder offset is intended to create less friction between the cylinder wall and 2mm-larger piston on the power stroke. The cylinder is placed 12mm bike-forward for a more vertically oriented crankshaft connecting rod push (0.5mm shorter rod length/2.6mm shorter stroke) on the piston, squeezing maximum efficiency during combustion with less friction. The compression ratio has been bumped from 12.3 to 12.5:1 for more bottom-end power.

Higher on the food chain is an all-new cylinder head, again reversing course and dropping a valve from the process. The airbox is located below and behind the steering head, and from there the intake charge takes a downward path into the combustion chamber. Instead of the previous YZ's three intake valves, this new one uses a head with two intake poppets, marking an abandonment of Yamaha's five-valve configuration – four titanium valves are now used. The downdraft inlet path mates to an R1/R6–style fuel injection for a purported benefit to low- and mid-range combustion and torque.

Pumping life into the new engine is an easily tunable, battery-less Keihin electronic fuel-injection system and 44mm throttle body with a 12-hole injector for finer atomization and cleaner combustion at any altitude. The EFI’s open-loop system has seven sensors (for throttle position, intake pressure, intake air temp, air pressure, crankshaft position, coolant temp and g-shock) and can automatically alter fuel delivery by almost 50 percent.

Taller riders might find the cockpit of the new YZ a little tight, but it's easily rectified with a quick forward adjustment of the handlebars.
Two days of riding and 8 quick bolts get you inside the relocated airbox for cleaning.

One note about that G-sensor: Yamaha is the only OEM using such device. It’s designed as a safety feature to kill the engine when the bike leans past 45-degrees for more than 10 seconds. They’ve provided enough time for a double backflip, but as a crash and tip-over protection, it's like what you’ll find on many fuel-injected streetbikes.

And if that’s not enough, Yamaha’s accessory handheld, battery-powered GYTR Power Tuner ($289.95) makes changing air and fuel mixtures for different rider and track conditions a snap. Adjusting air/fuel mix and ignition timing at nine different points (low to full throttle, and low to high rpm) without a need for a computer sounds like a godsend. While Yamaha didn’t have any units on hand for testing, Joey tells us that Yamaha’s product appears much easier to use than Kawasaki’s computer-tethered accessory tuner. A memory function can save up to 9 custom maps that can be built ‘off-line,’ while traveling for instance.

The reconfigured engine allows the forward-facing air filter to get fresh air through a straighter intake path, breathing in less dirt and sand as seen with the typical airbox placement ahead of the rear wheel. While not quite a “ram-air” flow path, the bodywork’s radiator shrouds are designed to catch oncoming air that helps produce power.

Post-production gasses slip out the engine’s back door through a resonator and into the tornado-style exhaust header. The twists and bends add power-building length while actually appearing shorter. Hidden beneath the saddle and subframe, the 1000mm total length exhaust system is quiet at low revs, but a twist of the wrist lets loose the ferocious bark of the 450F. Launching toward the finish line, this ain’t no trail bike, as the 2010 YZ450 is all about racing. More than 50 GYTR accessory products will be available from day one.

Other engine goodies include an easier to check engine-oil sight glass. No more wiping your dipstick on your sock to check the dry-sump levels. Oil volume is the same as the ’09.

The engine changes made a positive impression on our test rider. “It definitely has a lot more power and is more rideable than last year,” says Webb, adding that its low-to-midrange power is a noticeable improvement.

Cradling all that new technology is a 16-piece forged, cast and extruded aluminum bi-lateral beam frame. Gone is the y-shaped frame of 2009. Instead, the “double-S’ design differs from last year's construct while maintaining the same rake and trail, offering more stability and consistency to spring bank under impact loads at any speed.

The fully kitted GYTR YZ450F will run you about $5,000 extra, with everything from clutch kits, performance exhaust, high-compression pistons, camshafts, and cosmetic goodies. The list of more than 50 items is entirely CAD-designed and Yamaha tested.

Straddling the frame’s twin spars is a hinge-mounted translucent gray gas tank that allows for visual fuel checks. The majority of the tank is tucked beneath the 39.3-inch-high saddle for greater mass centralization and cornering ability. A fuel pump built into the tank itself contributes to a capacity reduction from 1.85 to 1.6 gallons, but Yamaha says it's still enough to get through a long moto because the injected engine is more efficient at burning fuel. The factory claims the YZ is able to run 60 minutes of race-pace riding.

The rotated engine configuration and resulting mass centralization yields light and tight handling and maneuverability, a clear distinction for our test rider who is accustomed to the previous YZ.

“It’s hard to ride at first,” remarks Joey, “especially when compared to my ’09 (YZ450F). But after a few adjustments and a full day of riding, the changes are noticeable – much appreciated.”

“It doesn’t turn like a Yamaha anymore…”

“It’s the most nimble handling 450 ever,” said Tim Olson, media relations manager for Yamaha’s off-road division, which Joey corroborated. “(Its handling is) Suzuki-like, without sacrificing any of its good ‘ol stability.” Joey added that the mass-centralization efforts made the YZ “feel very light out on the track and gave me the ability to direct the bike where ever I wanted.”

Steering quicker than the 2009 YZ, it took Joey a few laps to adjust to the all-new design.

Standing tall, the KYB speed-sensitive front fork now has a 10mm longer stroke (310mm) and increased damping, a new oil seal shape and a new inner rod surface treatment.

In the rear, the swingarm linkage has been repositioned to put the larger KYB shock (50mm piston from 46mm) in balance and on centerline with the frame and swingarm for more consistent flex characteristics and rider feel. The larger piggyback reservoir helps increase low-speed damping by the same (approximately) 10% as the front for better bump absorption. The relocation of the airbox and intake mixers up front allowed for such freeplay down below. While the swingarm pivot bolt diameter shrinks 1mm to 17mm, the linkage curve remains the same as the ’09.

While the bike was set up for Joey’s 160-pound body, the YZ was still responsive and soaked up heavy hits without bottoming out when this 200-pounder hopped on for a few laps. The KYB shock kept the 19-inch Excel and Dunlop 120/80 rear tire planted and tracking no matter how rough the terrain.

J-Dub described the YZ's setup as “excellent and possibly the best stock suspension available right now. The suspension is getting completely used all the way through its stroke which makes for a better ride.”

Rider ergos are also designed to centralize the entire mass, and a flatter saddle lets a rider get farther up on the front wheel. The handlebar position has been pulled back 4mm and dropped 8mm, and the triple clamps have decreased in offset as well, from 25 to 22mm. That’s 3mm closer to the rider, and this tighter rider triangle was noticed by the riders at the event. Almost everyone rotated forward the 4-way adjustable Pro Taper bar, including our giraffe-like JW. Overall bike width remains the same as the 2009 units.

Making both the new YZ and MO look good, SoCal’s Joey Webb (#158) tore up Maryland’s Budds Creek MX track with ease.

Revolutionary? Best in class?

It’s been a great while since MO’s had a YZ report, but we’re turning over a new leaf just as Yamaha is hitting the market with its next industry disruption. In 2003, MO tested the first 449ccYZ450F. It's now making headlines again.

With an entirely new twin-beam frame, rotated engine design, adjustable fuel injection, extreme mass centralization and new styling, the 2010 YZ450F is sure to turn heads if not losers into winners.

“It's leaps and bounds better than last year's YZ, that's for sure,” Webb assures. “Its handling doesn't even feel like a 450. It feels closer to a 250. ”

But is it enough to challenge the excellent new KX450F? In terms of power, Joey says “the Kawasaki still has it beat.” But he adds that the YZ has an edge in the way it handles and steers, “feeling lighter and more predictable in the corners.”

The new YZ is available in two colors: Team Yamaha Blue/ White for $7,990 and a White/Red combo with black wheels and a gold chain for $8,090.

Related Reading
Yamaha Sketches out the Features on the New 2010 YZ450F
2010 Yamaha YZ450F Preview
2010 Kawasaki Kx450F Review

Alfonse Palaima
Alfonse Palaima

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