New for 2019, the KX450 becomes Kawasaki’s first motocross bike with an electric start, which is activated by the push of a button located on the handlebar near the right grip making starting easy and convenient. A lightweight, compact Li-ion battery helps keep weight down, as does an automatic centrifugal decompression system fitted to the exhaust cam, which lifts one exhaust valve to facilitate starting.
In addition to an electric start, the KX450 also becomes Kawasaki’s first motocross bike equipped with a hydraulic clutch. The new clutch offers a more direct feel and an easier pull for lighter lever action, helping to reduce fatigue while on the racetrack. 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 brought top-level road racing technology to the KX450 valve train, using designs from Kawasaki World Superbike engineers. It uses finger-follower valve actuation, enabling larger-diameter valves and more aggressive cam profiles. Thanks to the finger-follower valve actuation, the rev-limit has been raised, contributing to increased high-rpm performance. The change to finger-follower valve actuation reduces the valve train mass and friction compared to a tappet-style valve actuation. A DLC coating on the finger followers helps protect against wear.
Complementing more aggressive cams, larger 40 mm intake valves and 33 mm exhaust valves with increased lift help air flow and contribute to increased power. Valves are formed from lightweight titanium, reducing reciprocating weight and offering high-rpm reliability. Chromium steel valve spring retainers and a highly durable chromium nitride coating on the camshafts improve reliability at high-rpm. The lightweight bridged-box piston uses the same design as the Monster Energy® Kawasaki race team’s factory race bikes, contributing to strong performance throughout the entire rpm range. The revised piston design reduces weight and optimizes strength for durability.
The cylinder is offset 8.5 mm forward to reduce mechanical loss through friction from the piston movement, enabling more efficient power generation. A special coating used on the intake port cores during the casting process make ports ultra-smooth, which increases efficiency and performance throughout the rpm range.
The new header pipe length has been increased by 105 mm to match the updated engine package and improves 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 improves air flow, contributing to increased performance at all rpm. New downdraft-style intake routing allows an even straighter approach for intake air into the cylinder, improving cylinder-filling efficiency and contributing to increased engine power. The new 44 mm throttle body is now larger and features reversed orientation of the butterfly for better fuel atomization from the top mounted injector. A new fine atomizing, 12-hole injector now sprays 75 micron droplets and flows over 20 percent more fuel to contribute to increased power, smooth power delivery and superb engine response at partial throttle.
A close-ratio five-speed transmission features lightweight gears and shafts to keep weight down, yet retain strength, while contributing to the motorcycle’s winning performance. Revisions have been made to the shift drum and shift fork, resulting in a weight savings. The engine cases, which feature a scavenger pump on the right case, have been constructed of extremely light materials and are designed to meet the highest standards of durability. A change from needle bearings to plain bearings for the connecting rod big-end reduces mechanical loss, contributing to overall performance.
The new lightweight fuel pump is located in the plastic fuel tank and has a revised design that is more compact, enabling a flatter design for the top of the tank.