The headline feature for Kawasaki’s new KX450F is Launch Control, but don’t let that one item overshadow the extensive list of changes that transform this green machine into an all-new motorcycle. While Launch Control is cool, a redesigned frame, a heavily revised engine and a new electronics package are the updates that make the 2012 KX-F a better motocross bike.
Kawasaki invited Cycle World to try the new KX450F for ourselves at RedBud MX in Buchanan, Michigan, where we learned that you can feel the changes on this bike right at startup; Kawasaki has really nailed the starting procedure on its four-stroke MXers (although there is really no procedure to it). The KX is the easiest kick-starting 450 to date: It takes just one or two kicks, possibly three max (without a lot of resistance from the lever), to light its fire. Give credit to the automatic compression-release system that provides 1.0mm of lift on the exhaust valves during the kick stroke, along with a large AC generator rotor that pumps some serious electrical power to the EFI system.
At the start line, Launch Control is engaged by holding down a kill-switch-type button for a couple of seconds, after which a flashing light lets the rider know that the system is activated. It works as soon as the rider drops the clutch by retarding the ignition timing to help the rear tire maintain traction on slippery surfaces (although Launch Control is not to be confused with traction control). The system then remains engaged in the first two gears and automatically shuts off when the rider shifts to third.
On the dirt starting pad at RedBud, using second gear with Launch Control engaged got the best results. The difference between having the system on and off is noticeable; if the clutch is released too quickly, Launch Control reduces wheelspin and won’t allow a huge wheelie. Fancy clutch work by a rider skilled in starting techniques, however, will still be tough to beat off the line. So, although Launch Control is a really clever feature that solves a common problem digitally, most riders would benefit more from an aftermarket holeshot device that compresses the fork. A combination of the two would be ideal.
Kawasaki was able to get more power out of the KX450F by means of new hardware and revised software. The piston, top piston ring, intake cam, throttle body and exhaust system all are new hard parts. The ECU is updated and allows the use of three pre-programmed maps: Standard, Hard (terrain) and Soft (terrain). Although these maps are built into the ECU, the rider must change out external couplers known as “wire jumpers” to activate them. Plug-and-play is simple, but a bar-mounted switch would be easier. Standard mode is actually pretty aggressive, allowing a good bottom-end hit and a strong midrange. The aggressive (Soft terrain) plug was actually too much: The power delivery is abrupt just about everywhere in the rev range. The mellower Hard setting seemed to be the best of the three, providing power that was smooth off the bottom and had just enough grunt though the midrange. It does finish with a softer top-end delivery, but that provided added control in corners that was worth the trade-off.
When those three mapping options aren’t enough, an accessory ECU Setting Tool is available that allows riders to create their own personalized maps. We tried a custom map that incorporated aspects of the Soft and Hard maps, and we really liked the results. It delivered power that was similar to Hard on the bottom (mellower) but had more overrev and was really aggressive in the top of the rev range, like with Soft; this made the bike very controllable exiting corners and seemed to mimic the rider’s throttle movements more accurately.
Our favorite aspect of the 2012 KX450F is the new frame. It’s 4mm narrower between the frame rails, and although that doesn’t sound like a lot, it is; the previous KX felt big—maybe even too big. The new bike’s narrower profile, along with a smaller tank, helps make the KX more compact and easier to control. But larger humans needn’t worry: Kawasaki has given the KX-F two-position-adjustable footpegs and four-position-adjustable handlebar clamps to accommodate a variety of rider sizes. What’s more, the fuel tank is lower and narrower to allow a nice, flat seat, which is better for rider mobility. We haven’t yet been able to weigh the new 450F, but Kawasaki claims 249 pounds fueled up and ready to ride. The bike feels neither exceptionally light nor heavy; it’s very controllable, but you’re not likely to forget that it’s a 450.
Overall, the KX450F handles decently and instills rider confidence to push harder each lap. But even though the bike whips through corners with ease, the front end is vague, almost as though it goes where it wants to go; it felt like we had to hold the bars tighter to keep the front wheel planted. Stability is just okay stock, so we lowered the fork 5mm in the triple-clamps to raise the front end, which eliminated some of the high-speed sketchiness. This took away some of the front tire’s grip in flat corners but greatly increased straight-line stability. We also firmed up the fork by adding five clicks of compression damping and reducing rebound by two clicks. This helped the fork flow over braking bumps without it also wallowing in corners. Photographer Jeff Allen—who rides at a pretty fast pace—preferred the standard recommended clicker settings.
After sampling the $8399 KX450F, we’re excited at the prospects for 2012 and the beginning of the electronic era of dirtbikes. We’ll have a more in-depth review in CW as soon as we get the KX-F back on home turf for a thorough thrashing.
|Engine Type||dohc Single|
|Bore x stroke||96.0 x 62.1mm|
|Front wheel travel||12.4 in.|
|Rear wheel travel||12.4 in.|
|Fuel capacity||1.6 gal.|
|Seat height||37.6 in.|
|Claimed wet weight||249 lb.|