For 2011, the best tool for the job is once again a green one – Kawasaki’s reworked and revised KX™450F.

Details & Features

At a glance…
• Massively powerful engine
• Revised suspension settings
• Improved shifting performance
• Revised seat
• Refined ECU settings
• Easier fuel injection calibration system access
• Still easy to start!

Engine Overview
• 449cc liquid-cooled, DOHC, four-stroke single
• Bridged-box bottom piston design offers optimal engine performance
• Reinforced crankcase is strong and durable
• A forward lean angle of 3 degrees puts the engine in the ideal position for maximum traction
• Tuned for a broad powerband with the torque curve set just under the wheelspin threshold
• High-acceleration cams help the engine rev quickly
• Maintenance-free automatic cam chain adjuster
• Large airbox flap helps prevent mud and water from entering

Bridged-box Bottom Piston
• Same design as used on our factory racers; offers improved performance at all rpm
• Lighter and more durable than traditional piston designs
• Short piston skirt features low-friction coating for reduced mechanical losses
• Reinforced external ribs for strength and durability
• Revised profile with fully flush internal bracing results in a lighter, stronger piston
• Short piston pin offers increased strength

Cylinder Head
• Compact head is only 100mm tall
• 36mm titanium intake and 31mm exhaust valves with aluminum spring retainers minimize reciprocating weight and cylinder height to help ensure reliable valve control at high rpm
• Double valve springs allow a short cylinder head height and help ensure stable valve operation
• Camshafts, lobes and tappet surfaces feature a soft-nitride treatment for long wear and high-rpm reliability

Crankshaft
• Crankshaft with high inertial mass helps maximize rear wheel traction
• Wedge-shaped crank web provides enough offsetting moment for a 60 percent balance factor – and is similar to the crank balance in Kawasaki’s factory race engines, resulting in reduced engine vibration, smoother power delivery and increased performance, with a noticeably snappier response at low rpm
• Crankshaft and connecting rod feature a special carburizing and quenching treatment to maximize rigidity

Digital Fuel Injection
• Self-adjusts to atmospheric changes for easier starting, sharper throttle response and optimized power and stability when jumping/landing
• It is not necessary to re-tune, or change any jets to suit climatic conditions like on a carbureted model
• Ultra-fine atomizing injector with 10 holes sprays particles with a droplet size of 60 microns for smooth power delivery and engine response throughout the throttle range
• 43mm throttle body uses a progressive throttle linkage to deliver airflow in much the same way as an FCR carburetor
• Using two linked shafts, the throttle body opens more quickly after reaching the 3/8 open position
• Lightweight throttle body is approximately half the weight of a FCR carburetor, saving over one pound in weight
• Fast-idle knob on the throttle body allows riders to increase engine speed when starting a cold engine
• Fuel injector set at 45 degrees, the optimum angle for mid-range power

High-performance ECU
• New ECU programming and revised settings offer improved response at low-to-mid rpm
• No battery needed; the engine can be started with only three rotations of the crankshaft using the electricity generated by a single kick of the starter
• The system delivers electricity to FI system in sequence: first the ECU, then the fuel pump, and finally the injector for quick, easy starting
• Starting can be accomplished in a single kick
• The compact, lightweight ECU, located on the front of the steering head behind the number plate, was designed specifically for motocross use. The fuel pump relay is integrated with the ECU to help cope with the shocks and vibrations of motocross riding

Optional User ECU Setting Tool
• Allows racers to reprogram the ECU’s data maps for volume of fuel injected and ignition timing to alter engine characteristics to suit rider preferences
• The tool can also be used as a data logger, recording up to six hours of data, including engine rpm, degree of throttle opening, engine boost, coolant temp, air temp, ignition timing, fuel adjustments, gear position and system voltage

Lightweight Aluminum Fuel Pump
• Located in the fuel tank but at a new angle to help prevent damage in extremely rough riding conditions
• Features a rubber fuel filter cover that wraps around the inlet port and acts as a fuel trap to help ensure a stable fuel supply during vigorous motocross riding
• 1.9-gallon fuel tank is formed using a rotational molding process

Easy Starting
• Strong output from the large ACG rotor provides enough electrical power for the battery-less FI system to enable true one-kick starting without using a battery
• Equipped with an automatic compression release (ACR) system for quick and easy starting. The dual-weight centrifugal decompression system is fitted to the exhaust cam
• Compression release features 1.0mm of valve lift, to minimize the required kicking power
Efficient Cooling
• High-capacity Denso radiators feature tightly packed cores and a fin design that delivers superior cooling efficiency
• Radiators don’t need reinforcing brackets, which results in lower overall weight
• Shrouds feature a slim design that melds with the radiators’ design
• Radiator louvers feature four small blades set at a shallow angle for minimum overlap and maximum air flow

Strong and Durable Clutch
• Clutch assembly provides a direct feel and superb control
• Excellent oil drainage contributes to more direct feel
• Friction plates with substantial friction material contribute to a more direct feel
• Large operating plate pusher reduces the clearance between the pusher and the input shaft hole, improving clutch operation

Close-ratio 5-speed Transmission
• 5-speed transmission and low-rpm engine response combination offers riders more gear options for traversing rough sections or getting into the rhythm of a course easily so they can focus more on racing
• Thinner inner-link chain is light and strong
• Sprocket-style chain drive roller reduces the effect of driveline lash, helping smooth engine braking and facilitating additional corner entry control

Exhaust
• Short, one-piece stainless steel exhaust pipe contributes to optimum mid-high rpm performance
• Optimized exhaust routing contributes to improved ergonomics
• High-volume silencer helps meet noise regulations
• currently 94dB
• Right side panel has special passageway to help cool the silencer

Powerful Disc Brakes
• Rear brake pad material offers strong braking performance
• Powerful twin-piston hydraulic front caliper
• Lightweight semi-floating 250mm petal-type front brake rotor
• Single piston hydraulic rear caliper squeezes lightweight 240mm petal-type rotor

Light, Slim Chassis
• Revised engine mount brackets optimize frame rigidity for better handling
• Lightweight steering stem shaft contributes to light, nimble handling
• Main frame spars are 68mm tall and 24mm wide to provide an ideal balance between stiffness and compliance
• Weight-saving features include a slim head pipe, narrow cross-section and a downtube formed with a swaging (squeezing and hammering) process
• Swingarm pivot is located high in the frame to maximize rear wheel traction

Aluminum Swingarm
• Cross-section design contributes to light handling
• Tapered “D” shape swingarm provides ideal rigidity for excellent stability, and is lighter than a comparable
box-section unit
• Alloy swingarm features a cast front section, tapered hydroformed spars and forged chain adjusters
• Uni-Trak® rear suspension linkage ratio maximizes rear traction performance
• Suspension arm is mounted below the swingarm to allow a longer rear suspension stroke and more precise tuning

Front Fork
• Race-oriented suspension settings offer maximum overall performance
• Revised damping settings offer improved action and increased comfort during the initial phase of the
suspension stroke
• Kayaba Air-Oil-Separate (AOS) fork keeps oil and air in separate chambers for stable damping performance during long motos. Low-friction fork seals contribute to smooth action
• Diamond-like Carbon (DLC) coating on the outer surface of the inner fork tubes offers minimum stiction when the fork is exposed to lateral forces that would usually hamper slide action. The result is improved fork response, especially during cornering
• Friction-reducing Kashima Coat on the inside of the fork’s outer tubes contributes to smooth suspension action (especially at the initial part of the stroke) and a superb ride feel
• Wrap-around fork tube guards offer effective protection for the sliders

Rear Shock
• New damping settings contribute to increased stability and improved impact performance when landing from jumps
• Rear suspension settings and linkage ratios derived from extensive rider testing
• Kayaba rear shock features a large 50mm piston
• Rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately
• Also features Kashima Coat treatment on the cylinder for reduced friction and smoother suspension action
• Easy adjuster access for track-side suspension tuning

Rider Interface and Styling
• Dual injected two-tone, one-piece plastic shrouds and side number plates
• Optimized exhaust routing contributes to improved ergonomics
• Right side panel has special passageway to help cool the silencer
• Black plastic covers, triple clamps, engine covers, and black alumite-coated rims – just like Kawasaki’s factory teams
• Wide 50mm footpegs provide excellent feel and a comfortable platform
• Frame is wider at the ankles to offer optimum grip, narrows below the seat to allow a slim riding position
• Slim seat design uses firmer urethane foam that keeps its original shape longer for the best possible ergonomics and feel
• Seat has a slip-resistant top surface for good grip when seated and a new material along the sides for extra grip when standing

Additional Features
• Skid plate made of resin material offers great protection without excess weight
• Clutch cable boot features a large quick adjuster, making it easy for riders to adjust play in the clutch cable on the fly
• Increased front axle collar diameter transmits more feedback from the contact patch to the rider
• Ribless rear hub and butted spokes offer light weight and excellent durability
• Rear caliper guard helps protect the caliper from damage

Specifications

Engine: Liquid-cooled, four-stroke single with DOHC and four-valve cylinder head
Displacement: 449cc
Bore x stroke: 96.0 x 62.1mm
Compression ratio: 12.5:1
Fuel System: 43mm Keihin throttle body
Ignition Digital DC-CDI
Transmission: Five-speed
Rake / trail: 26.7 degrees / 4.6 in.
Front suspension / wheel travel: Uni-Trak® linkage system and Kayaba shock with 50mm piston,
22-position low-speed and stepless high-speed compression damping, 33-position rebound dampening and fully
adjustable spring preload / 12.4 in.
Rear suspension / wheel travel : Uni-Trak® linkage system and Kayaba shock with 50mm piston,
22-position low-speed and stepless high-speed compression dampening, 33-position rebound dampening and fully adjustable spring preload / 12.4 in.Front tire size: 90/100-21
Rear tire size: 120/80-19
Front brakes: Single semi-floating 250mm petal disc with dual piston caliper
Rear brakes: Single 240mm petal disc with single-piston caliper
Overall length: 86.0 in.
Overall width: 32.3 in.
Overall height : 50.4 in.
Wheelbase : 58.3 in.
Ground clearance: 13.2 in
Seat height: 37.8 in.
Curb weight: 249.9 lbs.
Fuel capacity: 1.9 gal.
Color Choices: Lime Green