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:
2008 Yamaha YZ450F
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.
2008 Yamaha YZ450F
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.
2008 Yamaha YZ450F
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.
“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.