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TECHNOLOGY


ENGINE

Factory Tuning to Keep Expert Riders at the Front of the Pack

Already ranked at the top of its class in numerous enthusiast magazine shootouts, for 2010 the KX450F receives a number of engine and chassis updates to ensure its winning potential.

The KX450F base package provides an excellent platform for experienced racers to win races in the top classes. Design of the highly rigid aluminium frame, suspension components and settings focused on delivering superb high-speed stability – 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. Feedback from factory racers resulted in a number of refinements that deliver increased high-rpm and over-rev performance. The new engine has specs on par with Ryan Villopoto’s KX450F racer. Also inherited from the racing world, a new piston with bridged-box bottom makes its first appearance in a mass-production machine. Finally, fine-tuning of the clutch results in improved clutch feeling.

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.

NEW - Rubber damper collar used for the rear silencer mount also contributes to increased durability.

NEW - Right-side crankcase is reinforced at the lower engine mount for increased strength and durability.

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 maximized for a greater part of the rev range.

The engine is almost upright (forward lean angle is 3o) to help place the bike’s centre of gravity in the ideal position for maximum traction.

A symmetrical 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.

Light weight 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.

NEW - Cylinder skirt was strengthened to match the increased engine performance.

NEW - New thicker (22 mm >> 32 mm), wider (120.2 mm >> 127.8 mm)radiators with increased fin and tube pitch are stronger, offer better resistance to mud build-up, and maintain cooling performance. Because the new radiators are stronger, 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 minimizes 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. Since 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.

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 crank shaft. 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.

NEW - New ECU operating programme and revised setting data offer improved response at low-mid rpm.

An optional KX FI Calibration Kit (containing KX Racing software, an ECU controller, mounting bracket and damper, harness and USB cable) allows racers to adjust engine characteristics (by rewriting actual data maps) to suit their preference. (In addition to the kit, a PC and 12 V battery are all that is required.) Please refer to the Appendix for more details.

The 43mm throttle body makes use of a progressive throttle link to deliver airflow in much the same way as would a FCR carburetor. 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 atomizing injector with 12 holes sprays particles with a droplet size of 60µ for smooth power deliver and improved engine at partial throttle.

The injector was set at 45o, the optimum angle for improved mid-range power.

Lightweight flat-bottom aluminum fuel pump is located in the plastic fuel tank.

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.


CHASIS

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 - Revised front fender is thicker and more rigid.

NEW - New chain with thinner inner links offers 20 g in weight savings.

NEW - The KX450F now feature Bridgestone tires (F: M403; R: M404)

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 tire would drive the bike forward (instead of causing it to squat).  For ’10 revisions to the frame and suspension components were designed to offer lighter handling, improved suspension action, increased comfort and greater cushioning when landing jumps.

Lighter-handling chassis

While the frame remains essentially the same as that of the 2009 model, a revised steering stem shaft and new swingarm offer improved handling.
New steering stem shaft with lower rigidity contributes to lighter handling. NEW - New steering stem shaft with lower rigidity contributes to lighter handling.

NEW - Swingarm with revised cross-section also contributes to lighter handling.

The alloy swingarm uses a cast front section, tapered hydroformed spars and forged chain adjusters.

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.

NEW - Revised linkage ratios for the New Uni-Trak rear suspension further increase rear traction performance.

Extensive rider testing was conducted to determine the ideal linkage ratios and rear shock absorber damping settings to achieve maximum rear wheel traction.


SUSPENSION

Race-Oriented Suspension

Kayaba AOS (Air-Oil-Separate) fork keeps oil and air in separate 9 chambers for stable damping performance during long motos. Low-friction fork seals contribute to smooth action.

NEW - Revised spring rate, revised damping settings and the less rigid steering stem offer improved action (especially at the initial part of the stroke) and increased comfort.

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 minimizes 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 shock spring rate and damping settings contribute to increased stability and offer improved cushioning when landing jumps.

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.


RIDER INTEFACE

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.

NEW - Formed using a double-injection moulding process, 2-tone shrouds contribute to the slim package. Fine-tuned to accommodate the new radiators, the shrouds feature a slightly slimmer design.

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.

NEW - The optimized pipe line of the exhaust contributes to improved ergonomics.

NEW - Slim seat features firmer urethane which keeps its original shape longer.

The seat uses a slip-resistant top surface for good grip when seated and smooth sides for excellent rider mobility.

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 unitized collar. The one-piece unit provides additional stability during throttle operation.

Lightweight short-length grips feature a pattern designed to provide excellent grip.


ADDITIONAL OPTIONS

An FI indicator lamp (available as an option) warns of any problem with the FI system.
Optional engine parts include magneto rotors with different inertias (8.5, 9.5 kg cm2; STD: 9.0 kg cm2).

Optional chassis parts include handlebar holder for a ø28.6 mm bar (STD: ø22.2 mm), aluminum and steel rear sprockets (+/-2T), solid petal brake rotors for wet races, and different springs for the front fork and rear shock.

An FI indicator lamp (available as an option) warns of any problem with the FI system.

SPECIFICATIONS


ENGINE

Type     Liquid-cooled, 4-stroke Single
Displacement     449 cc
Bore and Stroke     96.0 x 62.1 mm
Compression Ratio     12.5:1
Valve System     DOHC, 4 valves
Fuel System     Fuel Injection: ø 43 mm x 1 (Keihin)
Ignition     Digital DC-CDI
Starting     Primary Kick
Lubrication     Forced lubrication, Semi-dry sump

DRIVETRAIN

Transmission     5-speed, return
Final Drive     Chain
Primary Reduction Ratio     2.727 (60/22)
Gear Ratios: 1st     1.750 (28/16)
2nd     1.412 (24/17)
3rd     1.188 (19/16)
4th     1.000 (19/19)
5th     0.875 (21/24)
Final Reduction Ratio     3.846 (50/13)
Clutch     Wet multi-disc, manual

FRAME

Type     Perimeter, Aluminum
Wheel Travel: Front     315 mm
Wheel Travel: Rear     315 mm
Tire: Front     90/100-21 57M
Tire: Rear     120/80-19 63M
Caster (Rake)     26.7°
Trail     116 mm
Steering Angle (Left/Right)     42°/42°

SUSPENSION

Front: Type     48 mm inverted AOS-type telescopic fork
Compression Damping     22-way
Rebound Damping     20-way
Rear: Type     New Uni-Trak
Compression Damping     22-way (low-speed), 2-turns or more (high-speed)
Rebound Damping     22-way
Spring Preload     Fully Adjustable

BRAKES

Front: Type     Single semi-floating, 250 mm petal disc
Caliper     Dual-piston
Rear: Type     Single 240 mm petal disc
Caliper     Single-piston

DIMENSIONS

Overall Length     2,185 mm
Overall Width     820 mm
Overall Height     1,280 mm
Wheelbase     1,480 mm
Ground Clearance     340 mm
Seat Height     965 mm
Curb Mass     113.6 kg (250.4 lbs)
Fuel Capacity     7 litres

DETAILS

MSRP         $9,299

Colour         Lime Green