• 2018-KX450F

Fuel-injected 449 cm³ 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. Race-inspired tuning and parts like the high-performance bridged-box bottom piston (a mass-production first when introduced on the 2010 KX450F) ensure top-level performance right out of the box. First introduced in 2016, the offset cylinder and numerous changes to the intake system offer even more power, the exhaust system matches local regulations, and the accessory KX FI Controller enables map calibration without a PC. With a light chassis, the engine also benefited from a low weight design, both combine to produce an awesome motocross package.

Intake valves have a flat surface, with a slim throat angle and tight recess (similar to valves on supersport models) contributes to the awesome high-rpm performance. Air cleaner shape and silencer construction ensure that FIM and MA noise regulations are met.


The narrow frame contributes to a slim overall package with good ergonomics. The slim riding position facilitates control.

Previously an extruded part, the front down tube is now a combination forged/cast piece (front part is forged; rear part is cast). The combination of this design contributes to greater front-end feel.

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).


Aluminium perimeter frame is a narrow across the main beams, considerably lighter, and features revised rigidity contributing to greater front-end feel.

Width across the main frames is approximately 6 mm slimmer than the previous model.  This facilitates position changes, making it easier for riders to slide forward and backward.

The lighter weight contributes to the bike’s quicker handling.

Thick walls for the sub-frame (seat rails) offer increased strength. Slim aluminium 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.


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.


Two rear intakes (holes added under the rear of the seat) allow air to enter the engine more easily, contributing to improved response.


The inward-angled orientation of the radiators (turned in 10 degrees) allows the shrouds to be very slim.

Top of the fuel tank is flat and low, for a very smooth progression from the seat to the tank.  The flat design gives the rider greater freedom of movement when changing riding position, and facilitates sitting farther forward.


KX motocrossers have long drawn on works technology to offer riders the best possible performance right out of the box. Launch Control Mode is just one of the factory features that give riders an edge when lining up at the start gate.

The KX450F features a launch control system similar to that on our factory racers. With the simple press of a button, riders can activate a separate engine map designed to ensure efficient race starts in slippery conditions. (The Launch Control Mode map retards ignition timing, allowing tyres to gain grip in low-traction situations, and allowing riders to focus on their lines.)



Lightweight ECU was designed specifically to withstand the rigors of motocross racing. ECU contains three plug and play engine maps (plus a fourth for Launch Control Mode).  Settings for the three maps can be reprogrammed with the optional KX FI Calibration Kit.


KX FI Calibration Controller, a portable handheld calibration tool, enables riders to make changes to engine maps by plugging into the ECU without needing a PC or battery. Comes equipped with seven preset map settings.


φ43 mm throttle body is both compact and lightweight. Ultra-fine atomising injector with 12 holes sprays particles with a droplet size of 60 μm for smooth power delivery and improved engine response at partial throttle.


The KX450F features Showa’s SFF (Separate Function front Fork)-Air TAC (Triple Air Chamber). The works-replica fork is very lightweight and highly rigid, contributing to superior riding stability.  With settings chosen for high-level to expert riders, the new fork offers excellent shock absorption performance at high speeds, making it easier for racers to ride faster.

Low-friction seals, and valve settings deliver and easy fork movement, matching the pitching characteristics to the lighter chassis.

Fork inner tubes feature lower rigidity, idealised for the chassis.


A digital hand pump is recommend to make adjustments – see you Kawasaki Dealer for the preferred pump (part # 999A423). Talk with your Kawasaki Dealer to find the best settings to suit your riding.


The rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately. A self-lubricating alumite coating on the tank cylinder helps prevent wear abrasion, and reduces friction for smoother suspension action.

The New Uni-Trak rear suspension system mounts the suspension arm below the swingarm, allowing a longer rear suspension stroke. The long stroke design 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.

Linkage ratios were also chosen to suit the light chassis.



The minimalist bodywork and aggressive fender and front number plate designs ensure the 2018 KX450F remains the sharpest looking bike in the paddock.

  • Kawasaki’s in-mould graphics, used on the shrouds, result in an ultra-smooth surface and ensure the racy graphics are not easily damaged.
  • Rims are coated in black alumite – just like our factory racers.
  • Candy Lime Green Type II finish on the oil cap and the two plugs on the generator cover further contribute to factory looks.
  • Candy Lime GreenType II SFF-Air front fork caps.
  • Showa TAC-SFF inner fork tubes have a Super-hard titanium coating to helps resist wear and lower friction.
  • Candy Lime Green Type II adjusters on the rear shock absorber.
  • Black rear spring on the Showa rear shock.
  • Embossed design on the clutch cover designed to gradually appear as contact from riding boots wears off the paint.
  • Engine covers are finished in silver paint, further reinforcing the KX450F’s factory image.


Model KX450F  (KX450HJF)
Engine Type 4-stroke, liquid cooled, single cylinder
Displacement 449 cm³
Bore x Stroke 96.0 x 62.1 mm
Compression Ratio 12.8:1
Valve System DOHC, 4 valves 
Fuel System Fuel injection: ø43 mm x 1
Ignition Digital DC-CDI
Starting Primary Kick
Transmission 5-speed, return
Clutch Wet multi-disc, Manual
Frame Perimeter, aluminium
Wheel travel – front 305 mm
Wheel travel – rear 305 mm
Tyre Size-front 80/100-21 (51M)
Tyre Size-rear 120/80-19 (63M)
Suspension – front 49 mm inverted telescopic TAC (Triple Air Chamber) with adjustable compression and rebound damping
Suspension – rear New Uni-Trak with adjustable dual-range (high/low-speed) compression damping, adjustable rebound damping and adjustable preload
Brakes – front Single 270 mm semi-floating petal disc with dual piston caliper
Brakes – rear Single 240 mm petal disc with single piston caliper
L x W x H 2,195 x 820 x 1,280 mm
Wheelbase 1,495 mm
Ground Clearance 335 mm
Seat height 950 mm
Fuel capacity 6.3 litres
Curb Mass 108.8 kg (includes full fuel tank, all fluids at optimum levels)
Colour Lime Green