For the most part, Japanese manufacturers stick to a three-year plan with each generation motocross bike. Year one for an all-new or significantly changed model is normally followed up by two years of refinements and small improvements. Based on that pattern, we expected the 2019 Kawasaki KX450 to be an all-new model as the previous generation 450 was debuted in 2016. Back in April, we took a trip to Kumamoto, Japan, to check out the action and machinery at the All Japan National MX Championship series opener. And just as we had expected, the factory Kawasaki team had two all-new machines under the factory tent; piloted by Yoshitaka Arai and Makoto Ogata. Equipped with all-new chassis and bodywork, the SR450Fs that we saw in Japan also boasted electric start, hydraulic clutch systems, and engines that were outwardly different than the current powerplant. Lo and behold, our sources in Japan proved correct when the new model information about the 2019 KX450 (the “F” designation was dropped for 2019, as there is no reason to identify the motocross line as four-stroke since there are no more two-strokes) dropped, and everything about the machines we saw being raced in Japan trickled down to the new production bike.
We’ll start with the powerplant which boasts plenty of upgrades, starting with an all-new finger-follower valve train that was developed by Kawasaki’s World Superbike engineers, with larger intake and exhaust valves, more aggressive camshaft profiles, a new bridge-box piston, and a larger 44 mm throttle body (up from 43 mm in 2018). The intake system is now straighter and of a more downdraft orientation for a more efficient powerband, and breathes through a thinner, reshaped air filter and left-side airbox. The header pipe has been lengthed over 100 mm to add more low-end torque, and the mass of the muffler has been increased significantly to keep the exhaust note down. The engine is now brought to life by an electric starter that’s powered by a compact and lightweight lithium-ion battery. A new compact fuel pump has allowed engineers to create a low-profile fuel tank that is 20 mm lower and flatter in the seat/tank junction while maintaining the same 1.6-gallon capacity. For the first time ever, the KX450 comes outfitted with a Nissin hydraulic clutch assembly, which has a light pull and excellent feel at the lever. Kawasaki becomes the first Japanese manufacturer to include a hydraulic clutch on a motocross bike. Interestingly enough, KTM has relied on them for two decades. Two optional fuel maps are accessed by changing the ignition couplers: black for a smoother powerband on hard-packed tracks, and white for a harder-hitting setting when traction is idea.
The new engine is surrounded by an all-new chassis that has revised frame cradles and frame spar construction for revised rigidity character throughout the frame. New aluminum engine mounts, wider and more rearward-mounted footpegs, and a new swingarm with a greater flex characteristic round out the chassis changes. One interesting design feature on the new KX450 chassis is the off-center shock mounting design, which was necessary to accommodate the new, straighter intake system. The shock is now nestled just to the right of the center of the frame. Though there is no skidplate supplied with the bike, mounting tabs are included on the frame and they match up with the OEM 2018 skid plate. As it has for several years now, the KX chassis offers a wide range of adjustability with two footpeg mounting positions and four handlebar mounting options.
Showa suspension graces both ends of the KX450. The new coil spring fork is 49 mm in diameter, and hold a new 22 mm front axle, which is 2 mm larger than its predecessor. The larger front axle is designed to deliver a more precise front-end feel. No one is happier than us to see the horrible Showa Triple Air Chamber fork go, as it was the one component that held the older KX450F from earning more than one Bike of the Year award. Kawasaki and Showa claim that the fork boasts A-Kit technology; from the 39 mm compression piston and 25 mm cartridge cylinder to the 14 mm piston rod and titanium nitride lower fork tube coating and Dimplish upper internal fork tube finish.
Bringing the bike down from speed are a pair of Braking disc rotors – the front a semi-floating 270 mm rotor, and the rear a 250 mm petal-shaped rotor – as well as a redesigned front master cylinder that boats revised leverage ratios and has the hydraulic hose fitting mounted in a better-safeguarded location on the back of the master cylinder.
Finally, the all-new bodywork includes one-piece radiator shrouds that are slimmer between the rider’s knees, and smooth junctions between the shrouds, side panels, and rear fender. As mentioned earlier, the plastic fuel tank is flatter and 20 mm lower at the seat junction, which allows riders to slide forward with greater ease. The graphics are now molded into the radiator shroud, and will not peel or rub off from contact with the rider’s knees.
On The Track
As trivial as it may seem, bringing the big KX450 to life with the push of a button gave us a thrill. It should be noted that the electric starter system on the Kawasaki seems to have a more aggressive starter crank than those found on the Hondas, Husqvarnas, KTMs and Yamahas…it fires the KX450 up in an instant; even while the bike is in gear with the clutch pulled in. Pulling in the hydraulic clutch and clicking the bike into gear was equally thrilling. The Nissin hydraulic clutch has a softer feel at the lever than the Brembo and Magura units on the KTM and Husqvarna, respectively. Action on the track is excellent with great modulation and feel. Though it doesn’t have the familiar feel of a cable-actuated clutch, the Nissin unit feels much more traditional than the existing hydraulic units.
When manufacturers achieve power gains, it is often at the expense of another portion of the powerband, or in one specific area. That said, it is astonishing to feel how much low-end throttle response and top-end overrev the new Kawasaki enjoys. The new engine revs quickly with an authoritative bark right off idle, and the powerplant feels so free that it gives the bike a light, lively feel on the track. There is no big hit anywhere through the RPM range as the KX pulls strongly and smoothly throughout each gear and continues to pull ridiculously far before falling flat. Some of our testers enjoyed riding the bike aggressively and carrying each gear quite far, while others short shifted and lugged the motor with equal effectiveness. Truth be told, the milder black ignition coupler actually made the KX450 easier to ride aggressively without as much wheelspin coming out of corners thanks to the more tractable power delivery. Of course, the white coupler gives the KX450 a snappier, more-aggressive powerband that we found tougher to manage. We’re realists, what can we say?
The new chassis and suspension combine to deliver one spectacular-handling machine. The superior performance and feel of the Showa coil spring fork (in stark contrast to the Triple Air Chamber fork it replaces), combined with the revised rigidity character of the chassis and the larger 22 mm front axle; really improves the front-end traction and control that the bike enjoys while cornering. We haven’t seen any data, but our impression of the new KX is that though it still has a rearward weight bias, there is a greater percentage of weight distribution relocated forward than there has been with previous KXs. In short, the new KX450 can be steered through corners with confidence, and it is just as easy to rail through a tricky rut as it is to slide around the outside line with the rear wheel. The feel and performance of the Showa fork is so superior to that of the air fork it replaces, that it’s not worth the words it would take to compare and contrast. Instead, we will say that the A-Kit technology inside the new Kawasaki Showa fork could outperform the action of every other spring fork, Showa, Kayaba, or WP. Action is plush and predictable in the small chop, and the fork exhibits great control and predictability through the stroke. We feel that as delivered, the fork is plenty firm for larger or faster riders, and it stays up in the plush portions of its travel when not being compressed by a g-out or landing. Out back the shock is equally impressive, as it keeps the rear wheel on the ground and clawing for traction, and the back end of the bike tracking straight and true. The new shock preload ring adjuster is easy to operate and a huge technological leap forward from the old lock rings that were adjusted with a hammer and punch. Like the fork, the shock was easy to adjust for a wide range of riders. 104 mm of shock sag was as easy to obtain with a 175 lb. rider as it was with a rider 10 pounds heavier.
Ergonomically, the bike is svelte and seamless. The new bodywork feels slimmer between the rider’s knees and none of our testers encountered any snagging of their boots or knee braces. The way the plastic parts dovetail together so beautifully make previous KXs seem clunky in comparison. Power and modulation of the new Braking front and rear brake rotors is excellent. Truth be told we couldn’t tell that the rear rotor was now oversized, but it was apparent that the new front brake assembly packs much more stopping power.
All told, the all-new 2019 Kawasaki KX450 performs head and shoulders better than the bike it replaces. And now, thanks to the accouterments like electric start and a hydraulic clutch, it now has everything that some of its competition has, too. The KX450 may not be the lightest bike on paper, but on the track it feels light and responsive, with quicker handling than every before without giving up its traditional Kawasaki feel.
Is there a new sheriff in town when it comes to the 450 class? Time will tell. One thing is for sure, though…this year’s 450 MX Shootout is going to be very, very interesting!