[2012 KX450F] Just over a week after winning the 2011 AMA Supercross championship with Monster Energy factory rider Ryan Villopoto and the SX Lites West title with Pro Circuit’s Broc Tickle, Kawasaki announced significant improvements to its 2012 KX450F and KX250F motocrossers. Both machines will hit the market with industry-first technology never before seen on production MX bikes.
With the 450F, the headliner on the what’s new list is the Launch Control Mode, which allows the bike’s electronics to optimize traction out of the starting gate for improved sprints to the first turn. A switch on the left handlebar arms the system, which then regulates ignition timing in first and second gears to enhance rear-tire grip by reducing wheelspin. Once third gear is selected, the ECU defaults to the normal parameters of the ignition map pre-selected by the rider.The KX450 now has an advanced Digital Fuel Injection system that allows the rider to choose between three map options without the need to use a laptop or any other external device; all he has to do is plug any one of three different provided wire-coupler caps into a steering-head-mounted DFI connector. One cap makes the engine run on the standard fuel map, one links to the map for soft terrain and the other is for hard terrain. The rider can also custom-tailor the fuel and ignition settings on all three of these maps by plugging into the ECU with the accessory KX FI Calibration Kit.
Internally, the KX450F’s engine was refined to improve midrange and top-end performance. A low-friction coating on the piston help perk up throttle response, and intake cam lift was increased for better breathing and a slight bump in power production. The five-speed transmission features redesigned engagement gears (each with 4 engagement dogs instead of 3) for smoother, more-positive shifting. Heavier clutch springs cope with the engine’s increased torque output.
A new frame and adjustable rider ergonomics top the list of chassis changes. The aluminum twin-spar frame is 4mm narrower, which makes the big KX more slender between the rider’s knees for better control. The fuel tank is shorter and narrower, allowing a flatter seat and more room for the rider move around.
Another innovation never before seen on a production motocrosser is the two-position-adjustable footpegs. The “alternate” position lowers the pegs by five millimeters for taller riders or those seeking a bit more legroom. So, too, is the aluminum Renthal handlebar adjustable, offering a choice of four positions (via alternate triple-clamp mount points) to further tailor the ergos to each rider’s preference. An optional shorter shock-linkage tie rod lowers rear ride height by six millimeters.
As before, suspension consists of a Kayaba shock with a fat, 50mm piston and Kashima Coat surface treatments on its internals for reduced friction. A 50mm Kayaba Air-Oil-Separate fork has Diamond-Like Carbon coating on the inner stanchions and is clamped by revised triple-clamps. The 250mm, rigid-mount, wave-type front brake rotor is lighter to reduce unsprung weight.
Although we wouldn’t call the 2012 KX250F all-new, it did get a couple of significant engine improvements. Most noteworthy is the industry-first use of a secondary fuel injector on a production MX Single. The second injector is located right near the junction of the throttle body and the airbox, and it has the same per-cycle flow capacity as the primary one. Kawasaki claims that the addition of the second injector gives the engine a wider spread of power and produces a stronger top-end hit.
To accommodate these and other changes to the Digital Fuel Injection, the ECU was updated, as was the ignition system to provide a stronger spark. As with the 450, a KX FI Calibration Kit is available for the 250 and uses the same connector as the ’11 model.
Other engine modifications include an improved crankshaft (with better inertial balance), new surface treatments on the piston and cylinder walls, and transmission upgrades for more-positive shifting.
The Showa Separate Function Fork (with springing in one leg and damping in the other) was retained but the spring rate is now higher. The same route was taken with the shock, which gets a stiffer spring (up from 51N/m to 53).
» 2011 Kawasaki KX450F – New Bike File
» 2011 Kawasaki KX250F – New Bike File
» 2011 Kawasaki KX450F – First Ride
» 2011 Kawasaki KX250F – First Ride
» 2011 Kawasaki KX450F – Video
» Five Cool Things About the 2011 Kawasaki KX450F – Video
» 2011 Kawasaki KX250F – Video
» 2012 Honda MXers – First Look