2008 Yamaha YZ450F Preview

The bike that started the four-stroke revolution keeps moving forward with chassis and engine refinements that ensure the five-titanium-valved YZ450F remains at the head of the open-class pack.

Features

Key Features:

The bike that started the four-stroke revolution benefits from chassis and engine refinements that ensure the five-titanium-valved YZ450F remains at the head of the open-class pack.
Subtle modifications to the aluminum frame and suspension mean light, precise, confident handling at any speed.
New head and exhaust design delivers stronger low- to midrange power without sacrificing top end power.
Ready to race straight out of the crate—with a ProTaper aluminum handlebar in adjustable clamps, titanium shock spring, gripper seat, Excel rims, etc.
Five-speed gearbox provides maximum flexibility and the right gear for a wide range of riding environments.

New for 2008:

Revised intake port shapes, and revised intake and exhaust cam profiles increase combustion efficiency for improved torque and throttle response in the low- to mid-rpm range.
Micron-level adjustment of piston external diameter minimizes piston-to-cylinder clearance for reduced vibration and mechanical noise.
Adjustment of gear backlash between clutch primary gears and balancer gears achieves further mechanical noise reduction.
A new, larger-diameter titanium exhaust header with revised taper characteristics enhances exhaust efficiency.
First “punched cone” muffler ever on a production bike allows 35 percent length reduction and 270-gram weight reduction while meeting AMA noise regulations.
Matte black crankcase covers: light, strong and cool-looking.
Steering head pipe and steering stem are 5mm shorter; lower forged triple steering clamp is lighter—for enhanced handling feel. Swingarm pivot stiffness is revised to complement front-end changes and further lighten and improve steering/handling.
Changes to the shape of the outer fork tubes and revised internals result in improved damping and a smoother ride.
Optimized linkage ratio provides a smoother ride and enhanced rear wheel traction.
New, YZ250F-style, front-brake caliper (-220 grams) and a lighter disc remove unsprung weight and provide excellent stopping power. A new axle and collar remove additional weight.
A 120/80-19 rear Dunlop D756 knobby replaces the 110/90-19 for even more traction. A D742FA replaces the D739FAL front tire.
Wider footpegs provide excellent boot traction and rider comfort.

Engine:

449cc five-valve DOHC liquid-cooled engine is super-powerful yet tractable.
39mm Keihin FCR flat-slide carburetor with throttle position sensor (TPS) and leak jet delivers precise fuel/air mixture and instant throttle response.
Lightweight titanium valves and load-reduced springs minimize reciprocating mass for fast-revving, hard-hitting power delivery across the rev range.
Primary kickstarting with automatic decompression and convenient, handlebar-mounted hot start lever ensures easy restarts.
Large-capacity radiator is reinforced for greater strength.

Chassis/Suspension:

Extensively tested aluminum frame uses a mix of alloy castings, forgings and extrusions to produce a tuned-flex frame that makes the YZ the finest-handling motocross bike ever.
Speed-Sensitive System 48mm Kayaba fork places transfer control valves (TCV) above the fork springs, so that damping force is controlled by piston speed: Eliminating mid-stroke damping force changes provides a smoother, more precise ride.
Titanium-sprung, four-way adjustable rear shock with Kashima-coated internals reduces friction for fantastic compliance and great handling.
More weight savings come via two-piece (part aluminum, part plastic) engine protector plates and thin-walled engine guard construction.
Removable aluminum rear subframe constructed of square-section tubing for light weight and easy maintenance.
Lightweight front-wheel hub for reduced unsprung weight and increased durability.
Lightweight front- and rear-brake calipers with aluminum pistons and anti-bubble front master cylinder; wave-style rotors reduce unsprung weight and deliver strong stopping power.

Additional Features:

“Gripper” style seat cover gives excellent feel and control.
ProTaper aluminum handlebar for strength and performance.
Works-style clutch lever features oversize barrel adjuster for easy, on-the-fly adjustability of lever/cable play.
Repackable exhaust silencer.
Durable, comfortable handlebar grips.

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SPECS

Engine
Type: 449cc liquid-cooled DOHC 4-stroke; 5 titanium valves
Bore x Stroke: 95.0 x 63.4mm
Compression Ratio: 12.3:1
Carburetion: FCR-MX39 x 1
Ignition: CDI
Transmission: Constant-mesh 5-speed; multiplate wet clutch
Final Drive: Chain Drive

Chassis
Suspension/Front: Speed-Sensitive System inverted fork; fully adjustable, 11.8-in travel
Suspension/Rear: Fully adjustable single shock; 12.3-in travel
Brakes/Front: Hydraulic single disc brake, 250mm
Brakes/Rear: Hydraulic single disc brake, 245mm
Tires/Front: 80/100-21-51M
Tires/Rear: 120/80-19-62M

Dimensions
Length: 86.4 in
Width: 32.5 in
Height: 51.4 in
Seat Height: 38.9 in
Wheelbase: 58.8 in
Ground Clearance: 14.7 in
Dry Weight: 219 lb
Fuel Capacity: 1.8 gal

Other
Warranty: 30 Day (Limited Factory Warranty)
MSRP:

• $7,099 (Team Yamaha Blue/White) Available from July 2007
• $7,199 (White/Red) Available from July 2007