2021 KX450


The Bike that Builds Champions

With more Supercross and Motocross championships than any other manufacturer, the KX name is synonymous with winning. The KX450 motorcycle represents the flagship of the KX lineup, built with the sole purpose of dominating the track. Over the past four decades, we've learned what it takes to win and stay on top. Our dedication to building the ultimate machine is undeniable, and the KX450 represents this to the fullest.





The powerful 449cc engine features new friction reduction coating on the piston for increased engine performance.

Front Suspension

The 49mm Showa Coil Spring Front Fork combined with A-KIT Technology deliver excellent handling. Large-diameter inner tubes allow the use of large damping pistons for race-winning performance while a large-diameter front axle provides exceptional front-wheel traction.

Kashima Coat Forks

Kashima Coat creates a hard, low-friction surface on the outer tubes. The hard coating helps prevent wear abrasion on the inside of the tubes, ensuring the sliding surfaces remain smooth for a long time, while the outside is protected against corrosion. The lubricating material in the coating contributes to smoother suspension action.

Hydraulic Clutch

Revised construction for the hydraulic clutch includes replacing the clutch's coil springs with coned-disc springs. The result is a lighter clutch actuation and a wider engagement range. Larger diameter plates provide increased fade resistance.

Downdraft Intake & Large Throttle

Downdraft-style intake routing allows an even straighter approach for intake air. The intake air’s approach angle into the cylinder is 20°, improving cylinder filling efficiency and contributing to increased engine power.  Large-diameter (ø44 mm) throttle with reversed orientation  - it turns in the opposite direction to open – flows a greater volume of air, providing increased performance – especially at high rpm,  over-run – and driveability.

Engine Design

KX450 features a valve train designed by Kawasaki’s World Superbike engineers. Finger-follower valve actuation enables the use of large-diameter valves and aggressive cam profiles.

2021 KX450 piston


A short skirt, reinforced external ribs and the use of a bridged-box bottom, featuring internal bracing, contributes to a light, strong piston design. A light piston (243 g) reduces the reciprocating weight and contributes to the engine’s performance. A change from needle bearings to plain bearings to the connecting rod big-end reduces mechanical loss = better engine performance.

Electric Start

Being able to restart an engine quickly during a race can mean the difference between keeping your lead, or having to fight your way back through the pack. Kawasaki’s electric start on a motocrosser makes restarting the engine as easy as pushing a button. Starting is electric only, via a button located on the right grip.

Rear Suspension

The Uni-Trak rear suspension system features adjustable dual-range (high- and low-speed) compression damping, adjustable rebound damping, and adjustable preload. The result is optimal damping and rear-wheel traction.

Front Brake

Petal disc brakes are among the KX450’s numerous factory-style components. The stylish discs contribute to both sporty looks and a high-quality appearance. Oversized semi-floating 270 mm diameter front disc contributes to strong front brake force, as well as superb controllability. The front brake master cylinder offers better initial control, while contributing to overall braking performance.

Larger Rear Brake

A large-diameter rear disc 250 mm diameter matches the large front disc and contributes to stronger stopping power.

Lightweight Lithium Battery

Lightweight, compact Li-ion Battery helps keep the weight gain to a minimum.


Swingarm rigidity matched to the frame, contributes to increased rear traction. 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) are chosen so that the rear tyre drives the bike forward (instead of causing it to squat).

Adjustable Footpegs

Adjustable footpeg brackets enable riders to lower their footpeg position, 5 mm. In the lower position, centre of gravity is lowered as is the rider’s point of view. The wide footpeg design, offers excellent grip, superb feel, and making it easier to weight the pegs.


Adjustable Ergonomics

The upper triple clamp with two set of handle mounts offer riders a choice of four handlebar positions, from: 25 mm forward, 15 mm forward, STD and 10 mm back. Two footpeg positions allows riders to tailor their riding position to suit body size and preference.



KX FI Calibration Controller enables riders to make changes to engine maps by plugging into the ECU without a PC or battery. Comes equipped with seven preset map settings, a built in colour LCD screen, transfer and diagnostic cable SD card, user manual and carry case.

Slim Shrouds

Slim shrouds are positioned close to the frame. Being slim where they come in contact with the rider’s legs, the single piece shrouds are easier to hold on to. 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. Smooth engine covers are also designed to not impede rider movement.


With the press of a button, riders can activate a separate engine map designed to ensure efficient starts in low-traction conditions. The Launch Control Mode map retards ignition timing, allowing tyres to gain grip, and allowing riders to
focus on their lines.


Adjusting engine settings to suit conditions is simple with the three DFI couplers. Plug-and-play style system is quick, easy and stress-free. Each of the three maps can be reprogrammed using the optional KX FI Calibration Kit.

  1. MX Hard conditions (default)
  2. MX Standard conditions
  3. MX Soft conditions.


Top of the fuel tank is designed to allow a flat progression from the seat to the tank, which gives the rider greater freedom of movement when changing riding position. The top surface is slip-resistance for seated grip.

Wheels and Tyres

Based on feedback from our factory race teams, the KX450 features a large-diameter front axle shaft 22 mm diameter, which contributes to greater front-end traction. Dunlop MX3S tyres contribute to increased front and rear traction.

2021 KX450

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KX450  (KX450J)

Engine Type4-stroke, liquid cooled, single cylinder
Displacement449 cm³
Bore x Stroke96.0 x 62.1 mm
Compression Ratio12.5:1
Valve SystemDOHC, 4 valves 
Fuel SystemFuel injection: ø43 mm x 1
IgnitionDigital DC-CDI
StartingElectric starting
Transmission5-speed, return
ClutchWet multi-disc with Brembo hydrualic operation
FramePerimeter, aluminium
Wheel travel - front305 mm
Wheel travel - rear305 mm
Tyre Size-front80/100-21 (51M)
Tyre Size-rear120/80-19 (63M)
Suspension - front49 mm inverted telescopic spring fork with adjustable compression and rebound damping
Suspension - rearNew Uni-Trak with adjustable dual-range (high/low-speed) compression damping, adjustable rebound damping and adjustable preload
Brakes - frontSingle 270 mm semi-floating petal disc with dual piston caliper
Brakes - rearSingle 250 mm petal disc with single piston caliper
L x W x H2,185 x 820 x 1,265 mm
Wheelbase1,485 mm
Ground Clearance340 mm
Seat height955 mm
Fuel capacity6.2 litres
Curb Mass110.2 kg (includes full fuel tank, all fluids at optimum levels)
ColourLime Green
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