Racing

2011 Kawasaki KX450F - Dirt Rider Magazine

May 25, 2010

In the 450cc motocross game, the only thing that matters to serious racers is top-tier performance and running up front. And for 2011, the best tool for the job is once again a lime green one - Kawasaki's reworked and revised KX™450F. In this arena you can't stand still technically, which is why Kawasaki engineers scrutinized every system and component of the race-winning 2010 model and came up with a host of tweaks that'll have red, blue, orange and yellow wondering what hit 'em.The latest open-class KX starts with the primary pieces that allowed the 2010 KX to win more Supercross events than any other bike last year - a brutally fast 449cc DOHC four-stroke single packing a broad spread of power housed in a lightweight-yet-strong aluminum frame connected to a suspension designed to offer compliance, high-speed stability and whoop-sucking performance all moto long. It was an ideal platform on which to win the majority of races in 2010, and that trend promises to continue with the revised, even faster 2011 model.Last year, the KX450F featured a number of engine refinements, including the first ever production use of a bridged-box-bottom piston (more high-end power and better over-rev characteristics), revised cam timing for better mid- and top-end performance and a reinforced cylinder sleeve and crankcase for improved durability.This year there's even more. Piston shape, for instance, has been modified to meld with the upgraded, higher-volume muffler, which is quieter than last year's unit. The ECU has been tweaked to provide a hotter and longer-duration spark for improved low-rpm response. The shift mechanism incorporates a larger internal roller and stronger shift-spring tension for more positive shifting. Finally, the fuel-injection system's Calibration Kit software has been updated, while the controller harness and connector have been modified for easier use.Changes in the chassis department are equally impressive, and show the results of our race team's effect on development. First up are revisions to the engine mount brackets that optimize chassis flex and improve handling. Next, the engineers revised the damping settings for the massive fork tubes for even better performance. For that factory-bike touch there are also blue-anodized compression damping adjuster caps in place of last year's silver ones. Damping settings on the rear shock have also been revised, and it, too, gets a blue-anodized compression adjuster. The seat features a new side-surface texturing for increased rider grip while aboard, and the drive chain guide has been thoroughly beefed up for increased durability; testing shows it to be nearly three times more durable than the unit fitted to the 2010 machine.The race-ready engine is compact and light, with a short 100mm cylinder head and a 12.5:1 compression ratio. A wedge-shaped crank web offsets 60 percent of the crankshaft's reciprocating weight, producing an effective "counterweight" effect. This is on par with Kawasaki's factory racers and helps reduce engine vibration, smooths power delivery and enhances low-rpm throttle response. A stainless steel exhaust pipe connects to the revised silencer, which uses long-fiber packing material to maximize service intervals. A rubber damping collar in the rear silencer mount provides a boost to long-term durability. The KX450F's Digital Fuel Injection (DFI®) automatically adjusts to suit track and climate conditions, and offers stable fuel metering even when landing from jumps in tough motocross conditions. The DFI system includes a compact and lightweight ECU, a 43mm throttle body, a lightweight aluminum fuel pump and an ultra-fine atomizing injector. Set at a 45-degree angle for ideal mid-range power, the 12-hole injector sprays precise, 60-micron fuel particles for smooth power delivery and accurate engine response throughout the rpm range.Designed specifically for motocross, the KX450F's lightweight DFI system doesn't require a battery; the engine can be started within three rotations of the crankshaft using only the electricity generated through the initial stroke of the kickstarter.An optional ECU Setting Tool allows racers to select from several different ECU data maps, or fine tune a custom map that alters fuel injection and ignition timing to suit different tracks and conditions. 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 and air temperatures, ignition timing, fuel adjustments, gear position and system voltage.The engine's phenomenal power is delivered through a clutch that features an ultra-light operating plate with superb oil drainage and beefy friction plates. The entire assembly is designed to provide exceptional clutch feel and durability. The drive chain features thin inner links and a slight weight savings relative to typical designs to help boost acceleration. The revised suspension damping settings provide lighter handling, improved suspension action, increased comfort and greater cushioning when landing from jumps.The 2011 KX450F's D-shaped aluminum swingarm features a cross section with narrow ribs and thin walls. It pivots high in the aluminum frame to maximize rear wheel traction. Mounting the arm of the Uni-Trak® rear suspension linkage below the swingarm provides a long rear suspension stroke and facilitates precise shock tuning.Complementing the responsive chassis is a Kayaba Air-Oil-Separate (AOS) fork that offers precise cornering and sharp handling. The fork features a Diamond-Like Carbon (DLC) coating on the outer surface of the inner fork tubes to minimize stiction when the fork is exposed to lateral forces that would otherwise restrict slide action. The result is smooth and precise response, especially during cornering. Overall suspension action is extremely smooth due to a friction-reducing Kashima Coat treatment on the inside surfaces of the outer fork tubes and the rear shock reservoir. Wrap-around fork guards provide excellent protection for the sliders.The 2011 KX450F's Kayaba rear shock's revised damping settings contribute to improved wheel control and impact performance when landing from jumps. It features a large 50mm piston and a Kashima Coat treatment on the shock internals to help maintain a plush feel throughout the toughest motos. Easily accessible dual compression adjusters allow high- and low-speed damping to be tuned separately, giving mechanics and riders the ability to easily fine tune the suspension for difficult track conditions.A slim seat design with firm urethane foam and a non-slip top and side surface provides even more seated and standing grip while retaining excellent rider mobility. The frame echoes the slim profile at the top, but widens at the lower end by the ankles to provide the rider with better feel and control. Completing the rider interface are wide 50mm footpegs that offer tenacious grip and a comfortable platform.The 2011 KX450F is available in Kawasaki Lime Green, with black alumite-coated rims and aggressive graphics for a factory appearance.Racers who ride their KX450F at designated events are eligible to receive support from Team Green™, Kawasaki's amateur racing support program. Each year, Team Green provides regional support vehicles and highly trained technicians at more than 100 events throughout the United States, offering technical information and assistance to those who race Kawasaki products. Kawasaki also offers a comprehensive contingency program for amateur and professional riders who place well at designated events.Kawasaki Motors Corp., U.S.A. (KMC) markets and distributes Kawasaki motorcycles, ATVs, personal watercraft, utility vehicles and recreation utility vehicles through a network of more than 1,475 independent retailers, with an additional 8,000 retailers specializing in Kawasaki power products and general purpose engines. KMC and its affiliates employ nearly 3,300 people in the United States, with 400 of them located at KMC's Irvine, California headquarters.Kawasaki's tagline, "Let the good times roll.™", is recognized worldwide. The Kawasaki brand has become synonymous with powerful, stylish motorcycles for over four decades. Information about Kawasaki's complete line of recreational products and Kawasaki affiliates can be found on the Internet at www.kawasaki.com.

2011 Kawasaki KX™450F****Features and Benefits

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 enteringBridged-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 strengthCylinder 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 reliabilityCrankshaft
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 rigidityDigital 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 powerHigh-performance ECU
New ECU programming and revised settings offer improved response at low-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 ridingOptional 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 voltageEasy 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 powerLightweight 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 processEfficient 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 flowStrong 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 operationClose-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 controlExhaust
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 94 dB
Right side panel has special passageway to help cool the silencerPowerful 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 rotorLight, 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 tractionAluminum 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 tuningFront 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 slidersRear 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 tuningRider 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 standingAdditional 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 damage2011 Kawasaki KX™450F 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 Injection: 43mm Keihin throttle body
Ignition: Digital DC-CDI
Transmission: Five-speed
Rake / trail: 26.7 degrees / 4.6 in.
Front suspension / wheel travel: 48mm inverted, Kayaba AOS with DLC coated sliders, 22-position compression and 20-position rebound dampening adjustment / 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: 90/100-21
Rear tire: 120/80-19
Front brake: Single semi-floating 250mm petal disc with dual piston caliper
Rear brake: 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: TBD lbs.
Fuel capacity: 1.9 gal.
Color: Lime Green
MSRP: $TBD
Wholesale distributor: Kawasaki Motors Corp., U.S.A.
9950 Jeronimo Road
Irvine, California 92618
(949) 770-0400
www.kawasaki.com