The Kawasaki KX450 (yes, Green is dropping the “F” from its naming convention) is all-new for 2019 and the main changes include a redesigned electric start-equipped engine, a hydraulic clutch, a Showa 49mm coil-spring fork, a new aluminum perimeter frame, and updated bodywork. Read on for an in-depth look at the host of changes made to the engine, suspension, and chassis of Kawasaki’s flagship motocross bike.
The all-new engine has been developed with input from the Monster Energy Kawasaki factory race team that, according to Kawasaki, has increased peak power and a flatter torque curve making it easier to get on the gas sooner. One of the biggest changes is the electric start-equipped engine, which makes the 2019 KX450 Kawasaki’s first electric start motocross bike. The electric starter is powered by a lightweight and compact lithium-ion battery, and an automatic centrifugal decompression system is fitted to the exhaust cam, which lifts one exhaust valve to help with starting.
In addition to an electric starter, this 450 also becomes Kawasaki’s first motocross bike to be equipped with a hydraulic clutch. According to Kawasaki, the new clutch offers a more direct feel and an easier pull for lighter lever action to help reduce fatigue while on the track. The hydraulic clutch is designed to provide a more consistent feeling through minimal change in clutch play as the clutch heats up during heavy use.
Kawasaki implemented designs from its World Superbike engineers on the KX450 valve train. It uses finger-follower valve actuation that enables larger-diameter valves and more aggressive cam profiles. Thanks to the finger-follower actuation, the rev limit has been increased for better high-rpm performance. The change to finger followers reduces the valve train’s mass and friction compared to a tappet-style valve actuation. A DLC coating is applied to the finger followers to help protect against wear.
Complementing the more aggressive cams are larger 40mm intake valves and 33mm exhaust valves with increased lift designed to help airflow and contribute to increased power. The valves are formed from lightweight titanium to reduce reciprocating weight and offer high-rpm reliability. Chromium steel valve spring retainers and a highly durable chromium nitride coating on the camshafts are designed to improve reliability at high rpm as well.
The new, lightweight bridged-box piston uses the same design as the Monster Energy Kawasaki race team’s factory racebikes, contributing to strong performance throughout the entire rpm range. The revised piston design reduces weight and optimizes strength for durability. The cylinder is offset 8.5mm (approximately 0.33 inch) forward to reduce mechanical loss through friction from the piston movement and enable more efficient power generation. A special coating used on the intake port cores during the casting process make the ports smooth to increase efficiency and performance throughout the rpm range.
The new header pipe length has been increased by 105mm (approximately 4.1 inches) to match the updated engine package and improve low-end power. A resonator chamber fitted to the exhaust system header effectively increases exhaust pipe length and helps reduce the decibel sound level. A new thinner air cleaner element is designed to improve airflow and contribute to increased performance at all rpm.
New downdraft-style intake routing allows a straighter approach for intake air into the cylinder and improves cylinder-filling efficiency and contribute to increased power. The new 44mm throttle body is now larger and features reversed orientation of the butterfly for better fuel atomization from the top-mounted injector. A new 12-hole injector now sprays 75-micron droplets and flows over 20 percent more fuel to contribute to increased power, smooth power delivery, and better engine response at partial throttle.
Revisions have been made to the shift drum and shift fork to make them lighter while the engine cases, which have a scavenger pump on the right case, have been constructed of lightweight materials and are designed to meet the highest standards of durability. A change from needle bearings to plain bearings for the connecting rod’s big end reduces mechanical loss, and the new fuel pump is located in the plastic fuel tank and has a revised design that is more compact and enables a flatter design for the top of the tank.
The digital fuel-injection system of the KX450 features a coupler package with three couplers to easily allow for the selection of preprogrammed fuel injection and ignition mapping to suit a particular riding style or track conditions. The four-pin DFI couplers select maps that are designed for standard, hard-, or soft-terrain settings. Changing the engine map involves connecting the coupler cap of choice.
For riders looking to fine-tune their ECU settings, the KX FI Calibration Kit is offered as a Kawasaki Genuine Accessory that is sold separately and provides access to the fully programmable ECU. The device can store up to seven preset maps and is PC-compatible. Another new feature for 2019 is that maps can now be changed while the engine is running by changing couplers, thereby eliminating the need to shut off the engine like on the previous models.
The 2019 Kawasaki KX450 has a new Showa 49mm coil-spring fork with A-Kit technology including large-diameter inner tubes enabling the use of large damping pistons designed to provide smooth action and firm damping. A hard titanium coating on the outer surface of the fork inner tubes helps prevent wear abrasion, and the increased surface hardness of the dark navy blue coating also helps to prevent scratches and damage to the tubes.
A Showa Dimplush finish process plus Kashima coat creates a micro-dimpled surface on the inner walls of the outer fork tubes to improve oil retention and helps prevent wear abrasion on the inside of the tubes to ensure the sliding surfaces remain smooth for a long time, while the outside is protected against corrosion. The A-Kit technology of the valving, surface treatments, and finishes are designed to provide smoother suspension action at the initial part of the stroke and a better overall ride feel. The Showa fork has 16 positions of adjustments on the compression and rebound adjustments.
The KX450 has a new Showa shock layout that has been shifted 5mm (approximately 0.2 inch) to the right to allow room for the new downdraft-style engine intake. Similar to the fork, the shock also has A-Kit technology, which includes a larger-diameter compression adjuster. The linkage ratios have also been revised to work in conjunction with the new shock, new aluminum frame, and new swingarm, and to keep the rear wheel planted.
The KX450’s chassis was developed by Kawasaki’s engineering team working closely with the factory racing team to develop a slim aluminum perimeter frame, designed to provide precise cornering through front end feel and agility at high speeds. As an evolution of the current design, the new frame has an increased overall rigidity balance.
The frame’s lightweight construction is composed of forged, extruded, and cast parts, while the engine is used as a stressed member and adds to the frame’s rigidity balance. The overall rigidity balance has been increased through a new steering head area with optimized rigidity, main frame rails with an updated cross-section, and a revised line for the swingarm brackets. The lower frame rails have been widened and also contribute to the bike’s overall rigidity balance. Forged chain adjusters are also equipped with a self-locking rear axle nut.
The KX450 features a new lightweight swingarm that has revised rigidity and was designed to match the frame, engineered to contribute to increased traction at the rear wheel. The alloy swingarm is constructed of a cast front section and twin tapered hydro-formed spars. With center of gravity and balanced handling in mind, engineers carefully located the dimension of the swingarm pivot, output sprocket, and rear axle, so that the rear tire would drive the bike forward.
The front brake master cylinder has been revised to offer better initial control while contributing to overall braking performance and consistency. The rear is equipped with a new larger-diameter 250mm petal-shaped Braking rotor that matches the large front disc and is designed to provide stronger stopping power. The rear brake master cylinder and hose have been revised to reduce weight as well. Derived from Kawasaki’s factory racing efforts, the KX450 uses a new larger-diameter 22mm front axle shaft intended to improve front end traction. The bike now comes stock with Dunlop MX3S tires as well.
The 2019 model has new bodywork that has been molded to match the V-mounted radiators and narrow chassis design. Each piece of bodywork has been designed to help facilitate rider movement with long, smooth surfaces that make it easy to slide back and forth. The new single-piece shrouds are slimmer where they come into contact with the rider’s legs, intended to make the bike easier to hold on to. The seams between the shrouds, seat, and side covers are nearly flush in an effort to increase bike control as well as moving around on the motorcycle.
The KX450 fuel tank is flatter, which allows the tip of the seat to be 20mm (approximately 0.8 inch) lower to give the rider greater freedom of movement when changing riding position and facilitate sitting farther forward. The bike comes with new lighter footpegs that are 5mm (approximately 0.2 inch) wider and positioned 3mm (approximately 0.1 inch) further rearward to make it easier to weight the pegs while the new engine covers are designed to be smooth to not impede rider movement as well.
The all-new 2019 Kawasaki KX450 has a claimed wet weight of 242 pounds, retails for $9,299, and is available now.