Details have emerged on perhaps the most hotly anticipated motocross motorcycle for next year: The 2010 Yamaha YZ450F. Off-road and motocross riding enthusiasts have been buzzing in anticipation of this new dirt bike and Yamaha hasn’t disappointed. Next year its top-of-the-line YZ machine is radically changed with an all-new engine and chassis.
For 2010 the YZ450F’s engine employs revolutionary new ideas we’ve never seen on a Japanese motocross bike. The first thing you’ll notice, besides its sharp new angular bodywork, is the way the 449cc liquid-cooled Single is positioned in the frame. It’s canted rearward for two reasons. First to exploit combustion force and second to keep the bikes reciprocating mass as centered and low as possible. You’ll also notice that the exhaust now exits from the rear of the engine. This was done in order to maximize the engine’s intake and exhaust efficiency by offering a direct path for both fuel and exhaust to flow through the engine.
The bike’s air intake system has been relocated to the front of the bike underneath the fuel tank just like on Yamaha’s YZF-line of sportbikes. A 12-hole fuel-injector shoots fuel into the 44mm Keihin throttle body attached to the front of the engine. It’s powered by a battery-less high input generator that is powered as soon as the kick start is touched.
The cylinder utilizes a bigger bore, shorter stroke format (97.0 x 60.8mm) with a higher compression ratio (12.5:1). A new 4-valve cylinder head replaces last year’s 5-valve component, and, in conjunction with the shorter piston stroke reduces the overall height of the engine. A new “tornado” exhaust system snakes trough the rear of the bike and is designed to complement the new engine’s power characteristics. The 5-speed transmission and cable-actuated wet clutch has also been updated for improved feel and shifting performance.
A new aluminum frame and swingarm are used, with the main frame constructed out of sixteen different pieces of aluminum designed to provide optimum rigidity and feel. The entire rear suspension was reengineered in order to keep the rear shock in the center of the machine, a position previously used by the airbox (now repositioned to the front of the motorcycle). Another big change is the way the 1.6-gallon fuel tank has been re-located under the seat between the frame rails.
Reworked triple clamps hold last year’s ultra-plush Kayaba Speed Sensitive fork and reduce offset down to 22mm (from 25mm). The fork also benefits from 10mm longer suspension stroke, updated damping characteristics and still offers both compression and rebound damping adjustment. The rear shock absorber, also made by Kayaba, gets a larger 50mm diameter piston and a larger volume gas reservoir. Like always, it offers adjustment for spring preload, high and low-speed compression, and rebound damping. Lastly, a new lightweight skid plate mounted beneath the engine helps protect the underside of the machine.
Factory GYTR Accessories
Yamaha is releasing an entire line of factory designed and tested accessories to complement your new YZ. Some of the most notable upgrades are the GYTR Ported Cylinder Head Assembly, (the same one James Stewart uses in AMA Supercross) and a GYTR Power Tuner. The handheld unit allows you to adjust your 2010 YZ450F’s engine settings including both fuel and ignition curves anywhere with a push of the button.
Pricing and U.S. availability has yet to be announced. Motorcycle USA will sample the new YZ450F later in September at the legendary Budds Creek Motocross Park in southern Maryland. Stay tuned for the full ride report.
The 2010 Yamaha YZ450F looks ready for dirt and we are looking forward to doing a full-test very soon.
2010 Yamaha YZ450F Specs
Engine: 449cc Liquid-cooled 4-Stroke Single; 4-valve
Bore and Stroke: 97.0 x 60.8mm
Compression Ratio: 12.5:1
Fuel Delivery: Fuel-injection
Transmission: 5-speed; cable actuation
Front Suspension: Kayaba Speed Sensitive; 2 way-adjustable for compression and rebound damping; 12.2 in travel
Rear Suspension: Kayaba gas charged shock absorber; 4-way adjustable for preload, high/low-speed compression, and rebound damping; 12.4 in. travel
Front Brake: 250mm disc with twin piston caliper
Rear Brake: 245mm disc with single piston caliper
Tires: 80/100-21 Dunlop D742FA, 120/70-19 D756
Seat Height: 39.3 in.
Ground Clearance: 15.0 in.
Fuel Capacity: 245 lbs.
Color: Team Yamaha Blue/White; White Red
Warranty: 30-days < br />