2008 Kawasaki KX450F

2008 MODEL

Refined Power Delivery for Improved Holeshot Performance

A host of improvements make the 2008 Kawasaki KX™450F motocrosser easier to ride and more reliable than ever. A newly-revised powerplant and improved shifting highlight the improvements made to the dominant AMA and World Supercross GP Championship winner.

With little doubt about the ample power of the KX450F, the 2008 engine received smoother, more user-friendly and linear low-rpm throttle response and torque delivery. These changes result in reduced fatigue, allowing riders to go faster for more laps. The improvements were achieved with new wedge-shaped crank webs, combined with a new heavier flywheel, resulting in reduced engine vibration and better low-end performance. Reliability of the engine was enhanced via a new connecting rod material with a harder surface, a revised gear ratio and rotor on the oil pump for increased oil circulation and the piston-cooling oil jet was redesigned to prevent oil from being trapped under the piston. 

The bottom end changes are coupled with a new shift cam shape and a wider track on the shift drum to permit easier and more consistent gear selection in the KX450F’s five-speed transmission. An ultra-smooth coating on the intake ports improves intake efficiency and throttle response, while revised ignition data provides easier restarting and a new five-bolt oil pump cover round out the engine upgrades.

Already a great handling motorcycle, the 2008 KX450F further benefits from new engine mounts spaced 10mm farther from the engine. This allows a slight decrease in torsional frame rigidity making for quicker turning and increased rear wheel traction.

Complementing the chassis change, the Kayaba fork and shock settings were fine-tuned to improve the front / rear balance for quicker turning and slightly stiffer settings were made to improve the bottoming characteristics. The overall suspension action is even smoother now through the addition of the friction-reducing Kashima Coat treatment on the inside surfaces of the outer fork tubes and the shock reservoir.

The 2008 KX450F will be available in Kawasaki lime green, with new black alumite-coated rims for a factory appearance, and aggressive graphics.

Engine
449cc liquid-cooled, DOHC, four-stroke single with lightweight, oxidized membrane treated titanium valves
High-acceleration cams help the engine rev quickly
Revised piston-cooling oil jet
Fifth bolt added to oil pump cover for improved sealing
Dual overhead, lightweight camshafts feature a soft-nitride surface treatment for long wear and high-rpm reliability
Special coating on the intake ports improve intake efficiency at all rpm
Titanium 36mm intake and 31mm exhaust valves with aluminum spring retainers and dual, progressive valve springs reduce reciprocating weight and cylinder height and help ensure reliable valve control at high rpm
Maintenance free screw-type automatic cam chain adjuster
Low-friction coating on piston skirt

Bottom End
New connecting rod material has a harder surface for reduced friction
New wedge-shaped crank web combined and a new heavier flywheel to reduce engine vibration and increased low-end performance
Oil pump has a revised gear ratio and 2mm larger rotor to increase oil flow
Unique crankcase breather system vents through the balancer shaft located in the crankcase, permitting the engine to rev more freely

Starting
Features highly reliable auto-decompression system; the dual-weight centrifugal decompression system fitted to the exhaust cam eases starting, and its simple construction helps to ensure reliability
Hot start system provides easier starts when the engine is hot, and the hot start lever is unitized with the clutch lever

Exhaust
New muffler joint bracket and thicker baffle plate help increase reliability
Large 41mm titanium exhaust header for increased power
Light weight, tapered head pipe with titanium heat shield helps increase exhaust efficiency over a broad rpm range
Silencer uses long-fiber packing for lower maintenance

Cooling
High-capacity Denso radiators deliver superior cooling efficiency
Slim radiators feature tightly packed cores and fins designed to enhanced heat dispersion

Shifting
The five-speed transmission received a new cam shape and a wider track (5.0mm to 6.5mm) on the shift drum to permit easier and more consistent gear selection

Brakes
Front and rear petal disc brakes help reduce unsprung weight
Disc shape helps clean the brake pads for more efficient braking performance
 
Frame
New engine mounts moved 10mm farther from the engine for a slight decrease in torsional frame rigidity to quicken turning and increase rear wheel traction
All-aluminum perimeter frame is a composite structure comprising forged, extruded and cast components
The slim profile of the KX450F frame, two-piece radiator shrouds that leave the upper frame spars exposed, and careful design of the remaining bodywork make the KX450F feel light and narrow beneath the rider
Works-style aluminum skid plate and plastic engine guards

Front Suspension
Kayaba AOS (Air-Oil-Separate) fork keeps oil and air in separate chambers for stable damping performance during long motos
New friction-reducing Kashima Coat treatment added on the inside surface of outer fork tube
DLC (Diamond Like Coating) on the fork sliders reduces stiction

Rear Suspension
UNI-TRAK® rear suspension system features revised shock valving to maximize traction for better front/rear balance, acceleration and enhanced controllability
The shock now features dual compression adjustability, for separate high- and low-speed damping tuning
A single, large port into the adjuster improves rider feel and adjustability over previous twin adjusters
New friction-reducing Kashima Coat treatment added on the inside of shock reservoir
Alloy swingarm uses cast front section, tapered hydroformed spars and forged chain pullers; the tapered spars are shaped to provide a balance of flex and rigidity required of the aluminum frame.
Sprocket style chain roller reduces drive lash

Wheels
32-spoke rear wheel for reduced unsprung weight
Lighter and stronger rear hub for increased durability and less unsprung weight
New black alumite-coated rims for a factory appearance

Weight Savings
Aluminum parts used instead of steel, including clutch cable elbow, clutch cable fitting nuts, fuel tank fitting nuts, seat mounting brackets, front brake hose clamp and igniter stay bracket

From the Cockpit
Renthal aluminum handlebars are standard
Lightweight short-length grips feature a special pattern to reduce vibration transmitted from the bars to the rider
Seat uses a slip-resistant top surface for good grip when seated and smooth sides for excellent rider mobility

Options
Different weight magneto rotors (+/-1 kg.cm2)
Handlebar Holder for a 1 1/8 in. bar (STD: 7/8 in.)
Aluminum and Steel Rear Sprockets (+/-2T)
Solid Petal Brake Rotors for wet races
Optional Rate Fork and Shock Springs
20” Front Wheel
Manual Decompression Lever & Cable