Kawasaki unleashes its revised KX450F and KX250F motocrossers for the 2015 model year.
Ryan Villopoto may not be able to contest this year’s Lucas Oil Pro Motocross Championship, but if you happen to spot him out and about, you can thank him for his part in making the 2015 Kawasaki KX250F and KX450F a pair of badass green machines.
Kawasaki unveiled its latest four-stroke motocrossers today, and while they aren’t radically different than the 2014 machines, they do benefit from key improvements learned aboard Villopoto’s 2013-AMA Motocross and 2014 AMA-Supercross title-winning Monster Energy KX450F factory bike as well as the KX250F’s of the factory-backed Pro Circuit Kawasaki team. Kawasaki engineers have carefully combed through both the KX250F and KX450F to enhance the power and increase their durability of their high-winding four-stroke engines, upgrade their Showa suspension, make their chassis lighter and slimmer and improve their braking components. Sounds like a recipe for success to us. Read on.
2015 Kawasaki KX450F, $8699
The KX450F’s 449cc, fuel-injected, DOHC, single-cylinder four-stroke engine really doesn’t need to make any more power to be competitive, and Kawasaki focused primarily on making key upgrades to its chassis, suspension and brakes. On the other hand, they didn’t elevate the status of the KX-F line by leaving well enough alone, either.
To that end, while the 2015 KX450F keeps the same 96.0×62.1mm bore and stroke of its predecessor, it has received a revised version of the F1 auto-style “bridged box” piston that it designed for the previous model. The new piston, which duplicates the one found in Villopoto’s factory bike, features short skirts with reinforced external ribs on the underside to improve its rigidity. Kawasaki says that the new piston’s slightly higher compression ratio of 12.8:1 (it was 12.5:1 in 2014), also gives the 450F motor a little more snarl, with a sharper mid-range hit and a more robust top-end feel than the 2014 model.
However, Kawasaki riders can tame the beast via Kawasaki’s revolutionary DFI couplers, which allow the rider to change the fuel-injection mapping from the Standard map to Hard or Soft maps in order to tailor the mighty KX-F to the track conditions or rider preference. The DFI coupler cap is easily accessible, so a power character change is easily accomplished in just a few seconds.
A revised ECU is also an update for the 2015 KX450F. New programming is claimed to enhance traction by quickly retarding the ignition when rear-wheel speed increases too quickly, such as from sudden, excess wheelspin. The ECU is still fully re-programmable—custom maps can be created with Kawsaki’s optional Kawasaki Racing Software Kit, the same tool used by Kawasaki factory and privateer teams in motocross and supercross.
Kawasaki introduced Launch Control to the motocross world, and now other manufacturers have begun to follow suit with similar systems. Kawasaki’s version works by retarding the ignition in first and second gears to increase rear tire grip in low-traction situations, such as when launching off of a concrete starting pad. The system is activated with the simple press of a button on the handlebar when the machine is in neutral, first or second gear. Once out of the hole, the system deactivates and returns ignition timing to the stock setting when third gear is reached.
Kawasaki also upgraded the KX450F’s front and rear suspension components for 2015, incorporating Showa’s latest Separate Function Fork (SFF) with a Triple Air Chamber (TAC). The SFF-Air TAC separates the damping forces into the left fork tube, while a pneumatic spring is housed in the right tube. The design is intended to provide less friction and is lighter in weight than a conventional spring fork.
The Triple Air Chamber fork features three separate chambers with individual air volumes that allow more precise adjustability via individual tuning. An inner 145psi high-pressure pneumatic chamber works in harmony with a 7.25psi low-pressure outer chamber and a 130.5psi high-pressure lower chamber to replace the conventional steel coil spring. Kawasaki says that the air spring setup does reduce oil contamination simply because there is no metal-on-metal contact to initiate friction. To make the suspension action even slicker, the SFF-Air TAC also uses a titanium coating on the inner side of the tube.
Suspension tuning with the Showa SFF-Air TAC is easily accomplished via a Kawasaki Genuine Accessories 0-300psi Digital Air Pump that is included with every KX450F. That, in and of itself, speaks volumes about Kawasaki’s effort to bring high value to its customers. Some other manufacturers with air fork-equipped models don’t even include a pump with their bikes! The pump’s digital display offers the rider a way to precisely tune the air pressures, and as an added feature, the casing handily stores the DFI Couplers for the fuel injection system. That’s not a bad feature, as we have lost a few modules and even unwittingly taken modules meant for another brand to the track.
Out back, the 2015 KX450F’s Uni-Trak linkage rear suspension gets a Showa piggyback reservoir shock with revised valving for improved damping in high-speed conditions to enhance the bike’s stability and resist bottoming when landing off of jumps. A slick Kashima coating inside the shock body is used to reduce friction and foster a smoother suspension action. Riders seeking even more suspension adjustment height may also want to opt for Kawasaki’s accessory rear suspension tie rod. The 1mm longer than stock rod lowers the seat height by 4mm.
The KX450F’s handling and chassis feedback is said to be improved for 2015 via tweaks to its aluminium perimeter frame, or, more to the point, its rear subrame. A lighter subframe has been incorporated to improve mass centralization for quicker handling and a more nimble feel in the saddle.
Kawasaki engineers have also fitted a new, 270mm oversized, petal-shaped front brake rotor designed in conjunction with world-renowned supplier Braking. The 20mm larger front rotor is paired with a 240mm Braking rear rotor, and both are petal-shaped to shed mud in sloppy riding conditions and maintain more consistent braking performance. The KX450F’s axles are also new for 2015, lightened by 31 grams up front and 32 grams out back.
The KX450F is already a pretty ergonomically satisfying 450cc machine, but Kawasaki engineers want it to be the undisputed comfort king, so its four-position upper triple clamp features two sets of handlebar mount slots to allow the rider a choice of four handlebar positions—25mm forward, 15mm forward, standard or 10mm rearward. Likewise, its footpeg brackets allow the rider to leave the footpegs in the standard position or lower them by 5mm. Additional comfort details include careful flush-fitting of the seams between the radiator shrouds, seat and side covers to help avoid riding gear snags for freer movement on the bike when transitioning from standing to seated, such as when cornering. The KX450F’s compact fuel tank is also designed to form a smooth straight line with the seat, allowing easy rider movement.
Last but not least, the 2015 KX450F also gets a new graphic treatment with a Lime Green finish and factory-style decals. Green-anodized engine plugs, oil cap and generator cover plugs, as well as green alumite suspension adjusters and black alumite wheels give the big KX an aggressive, factory fresh look that is expected to last, as the coated components are corrosion and scratch-resistant.
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