2019 KX450F, LIGHT & FASTER 450cc MOTOCROSSER
To maintain its edge in this fiercely competitive class, the 2019 KX450 benefits from a new engine mounted in its leanest chassis to date, enabling it to turn even quicker lap times, and make it the most powerful machine in the paddock. Complementing its already high performance, a number of new features – including finger-follower valve actuation, electric start and a hydraulic clutch, which are all firsts for a Kawasaki motocrosser – further elevate its race-winning potential.
Designed with mid-level to expert riders in mind, the KX450 motorcycle has always been built with one goal in mind: to put riders on the top step of the podium. And for over 40 years KX brand motocrossers have been extremely successful at doing just that.
Even More Powerful Engine
The new engine boasts an increase in peak power of approximately 2.5 kW (3.4 PS), while a flatter torque curve makes it easier to get on the gas. Finger-follower valve actuation (a valve train designed by Kawasaki’s MotoGP & World Superbike engineers) enables larger diameter valves and more aggressive cams. Downdraft style intake and reduced friction loss (care of new plain bearings for the connecting rod big-end) further contribute to the power gains. Being able to restart an engine quickly after a spill can mean the difference between keeping your lead, or having to fight your way back through the pack. Kawasaki’s first electric start on a motocrosser makes restarting the engine as easy as pushing a button. The electric starter is powered by a lightweight lithium ion battery.
Kawasaki’s first hydraulic clutch on a motocrosser offers more direct feel and lighter lever action. Less play as the clutch heats up during heavy use results in more consistent feeling.
Light Weight & Light, Nimble Handling
Complementing the powerful engine, light, nimble handling contributes to the KX450’s quick lap times. While the addition of electric start and the return to a coil-spring fork add weight, efforts were made to keep the weight gain to a minimum. The result is the KX450’s leanest chassis to date, and a highly-competitive, low overall weight of only 110.0 kg – a gain of only 1.3 kg.
Increased Front/Rear Traction
Matching the KX450’s increased power, increased front and rear traction ensure the bike can put power to the ground and get around corners quickly. A larger diameter front axle (a hint from our racing teams) helps at the front, while revised rear suspension layout and new linkage ratios benefit the rear.
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 first 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.
Large-Diameter Coil-Spring Fork
Handling suspension duties up front is a new high performance 49 mm inverted coil-spring fork. The large diameter inner tubes (the same size as on our factory racers) enables the use of large damping pistons, delivering smooth action and firm damping. A super-hard titanium coating on the outer surface of the fork inner tubes helps prevent wear abrasion. The increased surface hardness of the dark navy blue coating also helps to prevent scratches and damage to the tubes.
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 on the outside is protected against corrosion and for a factory appearance. The lubricating material in the coating contributes to smoother suspension action (especially at the initial part of the stroke) and a better ride feel.
Lightweight, Aluminium Perimeter Frame
An evolution of the current design, the new frame features revised rigidity and includes the engine as a stressed member. A new swingarm also contributes to the revised rigidity balance and increased rear traction.
Downdraft Intake & Larger Throttle
Downdraft-style intake routing allows an even straighter approach for intake air. The intake air’s approach angle into the cylinder increases from 10° to 20°, improving cylinder filling efficiency and contributing to increased engine power. Larger-diameter (ø43 mm >> ø44 mm) throttle with reversed orientation – it turns in the opposite direction to open – flows a greater volume of air, contributing to increased performance – especially high rpm and over-run – and driveability.
Advanced Engine Design
The change to finger-follower valve actuation reduces the valve train mass (IN is 4.2% lighter; EX is 7.9% lighter) compared to a tappet-style valve actuation (even taking into account larger-diameter valves). DLC (Diamond-Like Carbon) coating on the finger followers helps protect against wear. Complementing more aggressive cams, larger-diameter intake 40 mm diameter and exhaust valves 33 mm diameter with increased lift flow more air, contributing to the increased power. The camshafts benefit from a thin and highly durable gas-nitriding treatment for long wear and high-rpm reliability. Valves are formed from lightweight titanium, reducing reciprocating weight and offering high-rpm reliability. SCr (chromium steel) valve spring retainers contribute to increased reliability at high-rpm.
High Performance Engine
High-performance piston, featuring the same design used on our factory racers, contributes to strong performance at all rpm. A short skirt, reinforced external ribs and the use of a bridged-box bottom, featuring internal bracing, contributes to a light, strong piston design. Revised design and strength optimisation results in an even lighter piston (259.8 g >> 243 g), further reducing reciprocating weight and contributing to the engine’s increased performance. A change from needle bearings to plain bearings for the connecting rod big-end reduces mechanical loss, contributing to overall performance. Thinner air cleaner element restricts airflow less, contributing to increased performance at all rpm.
Longer header pipe (590 mm >> 695 mm) contributes to increased low end power and torque.
New Uni-Trak Rear Suspension
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. Revised linkage ratios contribute to increased rear wheel traction. Shifting the shock 5 mm to the right allows room for the new downdraft style engine intake. Revised rear shock layout also contributes to increased rear wheel traction. The rear shock features dual compression adjustability, allowing highspeed 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.
Complementing the KX450’s sleek new bodywork, factory-style graphics ensure it is the sharpest looking bike in the paddock and further reflect the KX450’s highly tuned performance. Green highlights on the suspension adjusters and engine oil cap and generator cover plugs contribute to a distinctive Kawasaki look.In-mould graphics used on the shrouds result in an ultra-smooth surface and ensure the racy graphics are not easily damaged. Aggressive design of the front fender adds to the racy looks. Rims are coated in black alumite – just like our factory racers. Fork and rear shock adjusters have a high-quality green alumite green finish on the oil cap and the two plugs on the generator cover further contribute to racy looks.
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. Revised front brake master cylinder offers better initial control, while contributing to overall braking performance.
Larger Rear Brake
A larger-diameter rear disc 250 mm diameter matches the large front disc and contributes to stronger stopping power. Revised rear brake master cylinder and hose are lighter.
Lightweight Lithium Battery
Lightweight, compact Li-ion Battery helps keep the weight gain to a minimum.
Swingarm rigidity was also revised to match the frame, and 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) were chosen so that the rear tyre would drive the bike forward (instead of causing it to squat).
New 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. Revised footpeg design is 5 mm wider (front-to-rear) and positioned 3 mm rearward, offering excellent grip, superb feel, and making it easier to weight the pegs. The new design is also lighter.
A choice of four handlebar positions and two footpeg positions allows riders to tailor their riding position to suit body size and preference. Upper triple clamp with two sets of handle mount slots and reversible handle mounts offers riders a choice of four handle positions to choose from: 25 mm forward, 15 mm forward, STD and 10 mm back.
Narrow and Flatter Seat
Bodywork designed to facilitate rider movement features long, smooth surfaces that make it easy to slide back and forth. Seams between the shrouds, seat and side covers are very flush, which facilitates control as well as moving around on the bike. Revised design for the top of the fuel tank top allows an even flatter progression from the seat to the tank. The flatter design gives the rider greater freedom of movement when changing riding position, and facilitates sitting farther forward. The seat uses a slip-resistant top surface for good grip when seated and smooth sides for excellent rider mobility. Seat urethane helps maintain the original shape longer.
Slimmer shrouds are positioned closer to the frame. Designed to be slim where they come in contact with the rider’s legs, the new 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 were also designed to not impede rider movement.
Launch Control Mode: The Holeshot Advantage
Even for top-level riders, controlling the massive power of a 450cc-class motocrosser off the start requires a high degree of throttle control and clutch finesse. By slightly reducing this power, Launch Control Mode helps riders maximise traction, increasing the chance of getting a good start. Launch Control Mode works in 1st and 2nd gear (and Neutral). Once the rider shifts into 3rd gear, the system is automatically disengaged, switching back to the normal engine map. System designed to the same specifications as that of our AMA factory racers.
Setting-Adjustable Motocross ECU
Adjusting engine settings to suit conditions has never been easier than with the KX’s DFI couplers. Plug-and-play style system is quick, easy and stress-free.Instead of a single engine map, the ECU features three (four, counting the Launch Control Mode map). Initial settings for the three maps are: Standard, Hard (conditions) and Soft (conditions). Using provided DFI couplers, riders are able to easily switch between the three maps to suit riding conditions. (Plug is conveniently located on the right side of the head pipe for easy access without having to remove any parts.) Maps can now be changed while the engine is running. ECU settings include programming that enhances traction by retarding ignition when the rear wheel speed increases too quickly (i.e. from sudden, excess wheel spin).
KX FI Calibration Controller (Accessory)
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.
Wheels and Tyres
Based on feedback from our factory race teams, the KX450 features a larger-diameter front axle shaft 22 mm diameter, which contributes to greater front-end traction. Dunlop MX3S tyres contribute to increased front and rear traction.