KAWASAKI KX 450F (2011)

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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. The bridged-box bottom 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 10-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 KX 450F model Highlights

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

Key Kawasaki KX 450F Technology

Technology PrintOverviewThe KX450F base package provides an excellent platform for experienced racers to win races in the top classes. Design of the highly rigid aluminum frame, suspension components and settings focused on ensuring control is maintained during high-speed riding – especially in straight lines – to enable race-experienced riders to ride full out. And to deliver holeshot-winning performance – a key factor that can mean the difference between running up front and winning, or getting stuck mid-pack – chassis geometry and the hard-hitting 4-stroke engine’s wide powerband were designed to maximise rear wheel traction. The combination is a proven race-winner, with Kawasaki racers regular podium finishers.

To keep the Lime Green racers out in front, Kawasaki engineers made a number performance-enhancing updates to both engine and chassis.
449 cc liquid-cooled, 4-stroke Single with battery-less fuel injection
Already featuring race-inspired tuning and parts like the high-performance piston with bridged-box bottom (a mass-production first when introduced on the 2010 KX450F), the 2011 engine receives further fine-tuning for increased low-end response, improved shift feel and other changes to meet stricter noise regulations.

Factory-inspired tuning
Works-base bridged-box bottom piston (unique Kawasaki feature used for the first time on a mass-production motocrosser on the 10MY KX450F) is just one of many features inspired by our factory racers.

Progressive throttle link
Lightweight 43 mm throttle body uses two shafts joined by a progressive link to give sharp response and excellent power feeling.

NEW Setting-adjustable motocross ECU
Lightweight ECU was designed specifically to withstand the rigors of motocross racing. Revisions to software and hardware offer improved response at low-mid rpm and improved combustion. The KX FI Calibration Kit contains KX Racing software, an ECU controller, mounting brackets and damper, harness and USB cable. In addition to the kit, a PC and 12 V battery are all that is required.

NEW Reduced noise
Changes to silencer internals ensure that stricter noise regulations are met.

NEW Improved shift feeling
Shift mechanism revisions result in a firmer shift feel.

High-precision ACR
Dual-weight centrifugal decompression system offers reliable starting.

All-aluminum perimeter frame
Slim aluminum perimeter frame is a lightweight construction composed of forged, extruded and cast parts.

NEW Lighter-handling chassis
Increased chassis flex, revised rigidity balance and new front axle collars result in lighter turning, increased rear wheel traction, a more planted feel from the front wheel and enhanced cornering accuracy.

NEW Uni-Trak rear suspension
Linkage mounts below the swingarm for more precise suspension tuning.

NEW Kayaba AOS fork with DLC coating and Kashima Coat
Diamond-Like Carbon coating reduces sliding friction for improved fork action, especially during cornering. Kashima Coat and high-precision machining further reduce friction. For ’11, revised settings offer improved action and increased absorption performance.

NEW Rear shock absorber
Dual compression adjustability offers a wide range of tuning options. Kashima Coat on the tank cylinder improves action. For ’11, revised settings offer improved action and increased absorption performance.

Renthal handlebar
A factory-style Renthal (standard-type) aluminum handlebar is standard equipment.

Slim rider interface
Bodywork components and seat designed to offer a slim, natural riding position making it easier for racers to go fast.

NEW Seat
Revised pattern for the seat sides offers more grip.

Petal brake discs
The KX450F features petal brake discs front and rear.
NEW Factory styling
Factory-style graphics, black alumite1 rims , Fork and rear shock adjusters have a blue alumite1 finish like our US factory racers.


Hard-Hitting Fuel-Injected Power
Fuel-injected 449 cc liquid-cooled, 4-stroke Single delivers hard-hitting power from low- through high-rpm. The broad powerband and responsive throttle offer a broad spread of torquey response that enables racers to get on the gas and go even from down low. In addition to the inherent benefits, fuel injection contributes to the KX450F’s lag-free acceleration, especially after landing jumps. Already featuring race-inspired tuning and parts like the high-performance piston with bridged-box bottom (a mass-production first when introduced on the 2010 KX450F), the 2011 engine receives further fine-tuning for increased low-end response, improved shift feel and other changes to meet stricter noise regulations.

Factory-racer engine tuning
- High-performance piston, featuring the same design used on our factory racers, contributes to improved performance at all rpm. A short skirt, reinforced external ribs and the industry’s only mass-production use of a bridged-box bottom, featuring fully flush internal bracing, result in a lighter, stronger piston.
- Wedge-shaped crank web increases offsetting moment for high crankshaft balance factor. At close to 60%, the balance factor of the ’11 KX450F is on par with Chad Reed and Ryan Villopoto’s factory racers. The high balance factor contributes to reduced engine vibration, smoother power delivery and increased performance – especially at low rpm, where response is noticeably snappier.
- In addition to generating the electrical output necessary to ensure easy starting, the large-diameter ACG also contributes to engine feeling at partial throttle.
NEW - Changes to the ECU programme and settings and revisions to the primary ignition circuit result in improved low-rpm response. Additionally, these changes lengthen spark duration for improved combustion.

Reduced noise
NEW - On North American models, revised internal construction results in a quieter silencer that clears stricter 94 dB noise regulations.

Improved shift feeling
NEW - Changes to the shift mechanism result in a firmer feeling when gears engage. The roller at the end of the position lever used to turn the shift cam ratchet has a larger diameter (16 mm >> 18 mm). Spring rate was increased 40% accordingly.

Battery-less fuel injection system
Designed specifically for motocrossers the fuel injection system incorporates a small lightweight ECU and operates without a battery to further eliminate unnecessary weight. And of course, fuel injection eliminates the need to adjust engine settings to suit track and climate conditions.

- Ensuring quick starting without a battery was a prime directive when developing the KX450F’s fuel injection system. Using only electricity generated by the kick starter, the engine can be started with only three rotations of the crankshaft. The system delivers electricity in the following order: 1) ECU, 2) fuel pump, 3) injector. With a warm engine, starting can be accomplished in a single kick.
- The compact, lightweight ECU, located just in front of the steering head (behind the number plate), was designed specifically for motocross use. To help cope with the shocks and vibrations of motocross riding, the fuel pump relay is built in to the ECU.
- The 43 mm throttle body makes use of a progressive throttle link to deliver airflow in much the same way as would a FCR carburettor. Using two linked shafts, the throttle body opens more quickly after the 3/8 open position, delivering sharp response and excellent power feeling.
- Ultra-fine atomising injector with 12 holes sprays particles with a droplet size of 60┬Ám for smooth power deliver and improved engine at partial throttle.
- The injector was set at 45°, the optimum angle for improved mid-range power.
NEW - Lightweight flat-bottom aluminum fuel pump is located in the plastic fuel tank. For ’11, the fuel pump mounting angle was rotated 55° to offer increased reliability.
- To ensure a stable fuel supply during vigorous motocross riding the fuel pump features a rubber fuel filter cover that wraps around the inlet port and acts as a fuel trap. A fuel return hose from the pressure regulator ensures there is always fuel in the fuel trap.

Factory KX FI Calibration Kit (optional part # 99999-0289 )
The KX FI Calibration Kit is the same kit used by Kawasaki’s works teams in Europe and the U.S. The kit enables expert riders to adjust engine characteristics (by rewriting actual data maps) to suit their preference, record riding data, and analyze their riding data to further fine-tune their settings.
- The KX FI Calibration Kit contains KX Racing software, an ECU controller, mounting brackets and damper, harness and USB cable. In addition to the kit, a PC and 12 V battery are all that is required.
- While the kit is designed to satisfy racers and expert riders, it is simple and hassle-free to use:
- the ECU controller mounts behind the number plate for easy access
- accessing the ECU is accomplished simply by connecting to a PC via the ECU controller using a USB cable (no additional switches are necessary)
- setting adjustments can be prepared in advance on a PC, or done when connected to the ECU
- the kit’s user-interface is simple to understand and easy to use
- The KX FI Calibration Kit contains seven preset settings that can be quickly and easily used to adjust the ECU to suit track conditions. The provided settings are shown below.

Setting Description
Richer fuel setting fuelling 5% richer than stock
Leaner fuel setting fuelling 5% leaner than stock
Advanced ignition setting ignition advanced 3° from stock
Retarded ignition setting ignition retarded 3° from stock
Hard riding surface setting ignition retarded, fuelling richer
Soft riding surface setting ignition advanced, fuelling leaner
Beginner setting engine power suppressed: ignition
retarded, fuelling richer

- For more advanced setting optimisation, the ECU maps for volume of fuel injected (via the FI adjustment window) and ignition timing (via the IG adjustment window) can be adjusted for given throttle position and rpm.
- Base settings are shown as a flat graph. Settings can be increased or decreased from the base according to rider preference.
- Multiple display options are available. Click [3D Graph] or [2D Graph] of the [3D/2D] to select the 3 or 2-dimensional display. When you use the [3D Graph], select [Surface Display] or [Frame Display] of the [3D Graph Type] to select the display type.
- Both click-and-drag (using the graph window) and numerical editing (using the map sheet) are possible.
- When connected to the ECU, the KX FI Calibration Kit can be used to display the status of a running engine. Information can be displayed in numeric form using the Data Monitor , or in visual form using the various display options offered by the Data Meter .
- The KX FI Calibration Kit can also be used as a data logger, recording up to six hours of data depending on the number of parameters (engine rpm, angle of throttle opening, etc) being recorded. After riding, the riding data can be viewed using the [Analyze] window . Parameters to be recorded and displayed can be selected independently.
- The logged data can lined up with the course layout to check actual riding, enabling more efficient FI settings to be determined. It also enables before-and-after comparisons and comparisons between riders.

For more detailed information on use and functions of the FI Calibration Kit, please refer to the KX FI Calibration Kit Instruction Manual.

Other performance-enhancing engine characteristics
- The engine was tuned such that the torque curve follows the limit of running resistance for as long as possible. (Unchecked, engine torque can exceed this limit, resulting in wheel spin, which does nothing to help forward momentum.)
- Efforts were made to achieve the widest possible torque band, so that traction efficiency would be maximised for a greater part of the rev range.
- The engine is almost upright (forward lean angle is 3°) to help place the bike’s centre of gravity in the ideal position for maximum traction.
- Asymmetrical high-acceleration cams yield high intake efficiency.
- During the cylinder head casting process, the cores for the intake ports were given a special coating to make the intake ports smoother. The extremely smooth surfaces that result increase intake efficiency at all rpm.
- Lightweight titanium valves (IN: 36 mm; EX: 31 mm) reduce reciprocating weight and offer high-rpm reliability.
- Aluminum valve spring retainers reduce reciprocating weight for reliable valve control at high-rpm.
- Double valve springs also help ensure stable valve operation and allow a short cylinder head height.
- 32 mm thick, 127.8 mm wide radiators with wide fin and tube pitch offer resistance to mud build-up while maintain cooling performance. The radiators are strong enough that the reinforcing brackets could be eliminated, resulting in lower overall weight.
- The screw-type adjuster on the cam chain tensioner is equipped with a pressure spring. Because the system automatically minimises the vibration caused by a loose cam chain, it greatly reduces the chance of a mishap during a race. (Non-automatic systems that are tuned incorrectly can actually adversely affect valve timing by putting too much pressure on the cam chain.)
- The combination of the smooth-shifting, close-ratio 5-speed transmission with the KX450F’s low-rpm engine performance offers the rider the option to shift to a higher gear when traversing rough sections. This reduces the effect of sudden (unwanted) throttle input, allowing focus to be given to racing rather than careful throttle control.
- In the event of a stalled engine during a race, getting it started again as soon as possible is a racer’s first priority, so the KX450F is equipped with an automatic compression release (ACR) system. The dual-weight centrifugal decompression system fitted to the exhaust cam eases starting in much the same way as a conventional lever-type system.
- Sprocket-style chain drive roller helps smooth engine braking by reducing the effect of driveline lash when the rider gets off the gas quickly and play in the lower side of the chain suddenly tightens. The additional control facilitates corner entry.

Factory-Style Chassis Components and Tuning
The KX450F’s slim aluminum perimeter frame is a lightweight construction composed of forged, extruded and cast parts. Chassis balance and settings were all set to suit race-experienced riders. The centre of gravity and key dimensions (swingarm pivot, output sprocket and rear axle locations) were chosen so that the rear tyre would drive the bike forward (instead of causing it to squat). For ’11 the chassis was fine-tuned, with revisions to frame and suspension components resulting in improved turning, greater rear wheel traction, more planted feel from the front wheel and enhanced cornering accuracy. The KX450F’s highly acclaimed high-speed stability remains unchanged.

Lighter-handling chassis
While the frame remains essentially the same as that of the 10MY model, revised rigidity balance results in a frame with moderate lateral flex.
NEW - Frame’s side hangers (engine mounting brackets), previously aluminum, are now formed from steel, and are thinner (t8.0 mm >> t4.5 mm).
NEW - The resultant increased lateral chassis flex enables lighter turning.
NEW - The revised rigidity balance offers a number of benefits:
- increased rear wheel traction
- more planted feel from the front wheel
- enhanced cornering accuracy makes it easier for riders to follow the line they want
NEW - Larger-diameter front axle collars (25 mm >> 27.5 mm) with higher rigidity contribute to the more planted feel from the front wheel.

Superior rear wheel traction
- The New Uni-Trak rear suspension system mounts the suspension arm below the swingarm, allowing a longer rear suspension stroke. The longer stroke in turn allows more precise rear suspension tuning.
- Extensive rider testing was conducted to determine the ideal linkage ratios and rear shock absorber damping settings to achieve maximum rear wheel traction.

Race-oriented suspension
- Kayaba AOS (Air-Oil-Separate) fork keeps oil and air in separate chambers for stable damping performance during long motos. Low-friction fork seals contribute to smooth action.
NEW - Lighter fork internals save 50 g each (100 g total).
NEW - Revised fork damping settings complement the changes to the frame and front axle collars, offering improved action and increased absorption performance.
- A super-hard DLC coating (Diamond-Like Carbon) on the outer surface of the inner fork tubes reduces sliding friction (and stiction) and gives better action, contributing to the smoother ride. The coating is even effective when the fork is exposed to lateral forces that would usually hamper slide action, such as during cornering. The increased surface hardness also minimises scratches and damage to the tubes.
- Friction-reducing Kashima Coat on the inside of the fork outer tubes contributes to smoother suspension action (especially at the initial part of the stroke) and a better ride feel.
NEW - Revised rear shock damping settings complement the changes to the frame and front axle collars, offering improved action and increased absorption performance.
- The rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately.
- The rear shock also features the Kashima Coat on the tank cylinder. The reduced friction smoothes suspension action.

Factory-style and other race-oriented components
- The KX450F features petal brake discs front and rear. In addition to helping reduce unsprung weight, the wave shapes of the petal discs help clean the brake pads for more efficient braking performance.
- Rear caliper guard protects the caliper from damage.
- A factory-style Renthal (standard-type) aluminum handlebar is standard equipment.
- Rib-less rear hub and butted spokes reduced unsprung weight.
- Rims are coated in black alumite1 – just like our factory racers.
NEW - Fork and rear shock adjusters have a blue alumite1 finish like our US factory racers.
- Factory-style graphics complement the KX450F’s highly tuned performance.

Rider interface
Designed with rider ergonomics in mind, bodywork components offer the rider a slim interface, the natural position making it even easier for racers to go fast.
- Formed using a double-injection moulding process, 2-tone shrouds contribute to the slim package.
- 2-tone side covers are also formed using a double-injection moulding process. Like the shrouds they contribute to the slim package. A hole in the right-side cover helps cool the silencer.
- The frame widens at the ankles to offer the rider better grip and narrows near the bend below the seat to allow a slim riding position.
- Optimised exhaust pipe line also contributes to the racer-friendly ergonomics.
- The seat uses a slip-resistant top surface for good grip when seated and smooth sides for excellent rider mobility.
NEW - Revised pattern for the seat sides offer more grip than before.
- Seat urethane designed to keep the original shape longer.
- Wide (front-to-rear) footpegs designed to offer grip and superb feel at the pegs.
- The clutch cable boot features a large quick adjuster, making it easier for riders to adjust play in the clutch cable.
- Throttle grip has a unitised collar. The one-piece unit provides additional stability during throttle operation.
- Lightweight short-length grips feature a pattern designed to provide excellent grip.

Engine
NEW - Changes to the piston profile result in reduced variance in piston clearance, contributing to improved exhaust emissions.
- Fast-idle knob on the throttle body allows riders to increase engine speed when first starting a cold engine.
- The crankshaft and connecting rod received a carburising and quenching treatment for additional rigidity.
- The camshaft lobes and tappet surfaces feature a soft-nitriding surface treatment for long wear and high-rpm reliability.
- A large flap inside the air cleaner case helps prevent the ingress of mud.
- The silencer uses long-fibre packing which is much more resistant to being blown out of the tail pipe than standard length packing. As a result, packing needs to be replaced half as often.

Chassis
- The alloy swingarm uses a cast front section, tapered hydroformed spars and forged chain adjusters.
- Designed to accommodate the in-tank fuel pump, the plastic fuel tank is formed using a rotational moulding (or rotomoulding) process that reduces weight.
- Large synthetic skid plate offers great protection with minimum weight.
NEW - Front chain guide (chain slider) uses a thicker plastic lining, offering longer wear life.

Other
- Optional engine parts include magneto rotors with different inertias (8.5, 9.5 kgfcm2; STD: 9.0 kgfcm2).
- Optional chassis parts include handlebar holder for a f28.6 mm bar (STD: f22.2 mm), aluminum and steel rear sprockets (48-52T; STD: 50T), solid petal brake rotors for wet races, and different springs for the front fork (4.6, 4.8 N/mm; STD: 4.7 N/mm) and rear shock (52, 56 N/mm, STD: 54 N/mm).
- An FI indicator lamp (Optional part# 23016-0049) warns of any problem with the FI system .

Specifications
MSRP: $8,149

ENGINE
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