The 2010 Yamaha YZ450F is no longer a rumor - it's officially here. After much speculation and anticipation, Yamaha finally unveiled the all-new YZ450F with its "backwards" motor, "curly fry" exhaust, and rearward-slanted cylinder. These drastic changes are designed to give the bike a lower center of gravity and more centralized positioning of weight, thus improving handling and cornering. The fuel tank, which actually holds slightly less gas (though we're assured it can still easily last a 40-minute moto), is now position underneath the seat.

The YZ is fuel-injected, via a 44mm Keihin, and has gone back to a four-valve (rather than five-valve) arrangement. It will again be offered in two colors - traditional Yamaha Racing Blue, and white/red (with black rims). The bike should start arriving at the dealers towards the end of the month. Pricing, however, has not yet been announced.

Yamaha also announced that it will again offer its YZ125 and 250 two-strokes for 2010.

Below is what Yamaha has to say about its "evolutionary" 2010 YZ450F...

FEATURES & BENEFITS

YZ450F's new rearward-slanted cylinder is a revolutionary advancement that achieves unmatched mass centralization, concentrating inertial mass toward the center of the machine. This bold new design also swaps traditional intake and exhaust positions, putting the lightweight airbox and throttle body out front. This contributes to mass centralization for nimble handling while also achieving a straight intake tract for superb combustion efficiency that delivers more power.

 

The cylinder is offset so the connecting rod is vertical at the moment of greatest combustion force, minimizing piston friction against the cylinder wall that could rob power. That means quicker response.

 

The new 4-titanium valve cylinder head is matched to a fuel-injection system developed specifically for the YZ450F. Instantly adapts to changing air/fuel mixtures depending on altitude and temperature, for an engine that delivers no matter what conditions.

 

The all-new aluminum Bilateral Beam frame provides a superb rigidity balance that complements the engine for unmatched lightweight handling and cornering. The result? The best cornering, most nimble 450F for all track conditions.

Revamped looks deliver new-generation styling, including front and rear fenders, intake cover, front fork protector, and number plate, along with the fuel tank and seat.

Accessory GYTR Power Tuner lets bike tuners adjust air/fuel mixture and ignition timing maps to match engine performance characteristics to the rider and track conditions.

All new for 2010

 

Engine:

 

The rearward-slanted engine allowed engineers to design straight intake and exhaust ports, creating the most direct path for air flow into the fuel-injected engine for incredible performance.

The YZ450F uses a battery-less fuel injection system with a 12-hole injector for superb fuel atomization. The 44mm Keihin throttle body is designed for easy starting, with an integrated cold start and idle speed adjustment knob. Yamaha FI provides optimal air/fuel mixtures in all altitudes and wide range of temperatures for outstanding throttle response.

14 volt/110W high output generator powers the battery less fuel injection system.

Four titanium valve cylinder head with a "pent-roof" design combustion chamber provides excellent combustion efficiency and unequalled power output.

Intake and exhaust camshaft profile changes to increase valve working angle and valve lift for most excellent performance at all rpm.

The bigger 97.0mm bore and shorter 60.8mm stroke, along with a higher 12.5:1 compression ratio, create a combustion chamber that delivers really impressive power.

The air filter case is changed to accommodate the new engine layout. Putting it up front keeps dirt and dust kicked up from the rear tire away from the intake system.

New "tornado-style" exhaust header with resonator efficiently scavenges exhaust gasses and helps the engine achieve its exceptional low-to-mid range torque characteristics, while the 150mm-longer muffler comfortably meets the latest noise standards without a sacrifice of power.

Clutch and transmission components have been thoughtfully revamped to give the rider great shifting feel.

Chassis/Suspenion:

The aluminum Bilateral Beam frame is crafted from a carefully chosen combination of forged and extruded aluminum, 16 components in all, for the right rigidity balance and light weight. A very symmetrical chassis design promotes nimble handling, letting riders enter and exit corners as quickly as possible to put the competition behind them.

New skid plate is constructed from tough polypropylene for great protection and low weight.

The swingarm and rear shock are redesigned, with the shock mounted along the central axis of the frame, taking advantage of the space no longer needed for the front-mounted airbox. This optimized combination delivers exceptionally linear performance for excellent bump absorption and awesome cornering ability.

The KYB Speed Sensitive front fork has 10mm longer stroke for excellent feel and shock absorption. KYB rear shock with large capacity piggy back reservoir and 50mm piston for more consistent damping control.

New fuel tank is positioned underneath the seat, contributing to the centralized mass. The seat is long and flat for to allow free rider movement.

New rear sprocket shape has a trick appearance and is light weight.

The triple clamps are redesigned, with a change in offset from 25 to 22 mm for unequalled cornering performance. The ProTaper bars are four-way adjustable to accommodate a wide range of riders.

The front and rear fenders, along with the number plate, side cover and front fork protector have been redesigned for an aggressive look. Less plastic is used to expose and enhance the lightweight aluminum frame.

SPECIFICATIONS

Model: 2010 Yamaha YZ450F

ENGINE

Type: 449cc liquid-cooled DOHC 4-stroke; 4 titanium valves

Bore x Stroke: 97.0 x 60.8mm

Compression Ratio: 12.5:1

Fuel Delivery: Yamaha Fuel Injection (YFI), Keihin 44mm

Ignition: CDI

Transmission: Constant-mesh 5-speed; multiplate wet clutch

SUSPENSION

Front: KYB Speed-Sensitive System, inverted fork: fully adjustable, 12.2-in travel

Rear: KYB fully adjustable single shock; 12.4-in travel

Brake/Front: Hydraulic single disc brake, 250mm

Brake/Rear: Hydraulic single disc brake, 245mm

Tire/Front: 80/100-21-Dunlop D-742FA

Tire/Rear: 120/80-19-Dunlop D-756

Length/Width/Height: 86.3/32.4/51.6 in

Seat Height: 39.3 in

Wheelbase: 58.7 in

Ground Clearance: 15.0 in

Fuel Capacity: 1.6 gal.

Wet Weight: 245 lbs

Color: Team Yamaha Blue/White; White/Red