2013 Kawasaki KX450F Spotlight
Produced by Kayaba (aka KYB), the 'Pneumatic Spring Fork' (PSF) is a revival of air suspension technology that has been an on-again-off-again feature of dirt bikes going back to the 1970s. However, the PSF on the 2013 KX450F takes the idea into the new millennium, offering a level of adjustability - and more importantly, easy adjustability - that arguably hasn't been seen before. The 2013 Kawasaki KX450F is billed as the first volume production motorcycle to feature PSF front suspension as standard. Honda's 2013 model CRF 450R will also feature the same suspension.
PSF works by replacing the main spring in each front fork with compressed air. Of course, removing the traditional fork spring saves weight. It's only 750 grams, but on a competition-focused machine like the KX450F, every bit of weight counts. Another benefit of the PSF is easier adjustability. Using the special adaptor, and a standard bike pump (although Kawasaki recommend using a pump with a built-in air gauge and flexible hose), the pressure can be easily changed to suit track conditions or individual riding requirements, without using tools, or having to disassemble the fork. This makes 'on-site' suspension adjustment much, much easier.
Eliminating the springs also reduces friction, by 20% according to Kawasaki, for smoother suspension operation. Removing the springs also allowed Kawasaki's designers to open up the diameter of the forks from ø24mm to ø32mm without adding extra weight. This greater area for the compression pistons increases bottoming resistance, and provides more stable damping force. Initial road tests of the KYB PSF say that while it takes a little getting used for those who are used to conventional spring suspension, the air suspension works well, while the ease of adjustability is a massive plus.
In conjunction with the PSF, Kawasaki also revised the rear suspension on the 2013 KX450F, revising the rear damping settings to complement the front forks. Mounting the Uni-Trak suspension system below the swingarm allows for a longer stroke, which in turn provides more adjustment options for suspension tuning. All up, the Uni-Trak rear features 33-way compression and 22-way rebound adjustment options.
For the KX450F's engine, the same basic 449cc single cylinder unit remains, but has been treated to a number of upgrades, over and above upgrades made to the 2012 model. Chief amongst these is a new high-performance piston, similar to that used on the factory race bikes. With a shorter skirt and a reinforced 'bridged-box' underside, the 2013-spec piston is lighter and stronger. In harmony with this, the piston's crown is lower, with sloped edges that Kawasaki say improve low and mid-range torque without alterations to the compression ratio. Modified intake cam profiles and revised ECU settings, in conjunction with the new piston, produce smoother power delivery and improved engine braking. The engine itself is canted forward slightly (3 degrees), in a similar fashion to Yamaha's back-slanted YZ450F engine. Kawasaki says this is the optimum position for traction.
Another feature on the 2013 KX450F that's sure to be a hit with racers is 'Launch Control Mode'. This feature debuted on the production models last year, and the push-button operation on the 2013 model is similar to that used on the factory race bikes. This activates a separate engine map, which retards ignition timing to ensure maximum grip in low traction conditions through first and second gears. Shifting into third gear returns the engine to its normal mapping. Separate to the Launch Control Mode are three plug-and-play style DFI couplers to adjust the engine mapping. With 'Standard', 'Hard' and 'Soft', the three ECU options allow for easy adjustability of engine mapping to suit track conditions like hard-packed dirt and soft, boggy sand.
Australian-spec versions of the KX450F feature low noise mufflers, in accordance with local noise regulations. This is achieved through holes in the pipe and baffle plate, along with pinched cut-outs in the silencer chambers and noise-absorbing pads between the air cleaner and rear guard. The 5-speed transmission was improved for smoother shifting on the 2012 model, so remains largely unchanged for 2013. Petal disc brakes feature a slightly revised design for the new model that's also lighter, with a new, pushrod-type front brake master cylinder and new pads.
The 2012 KX450F debuted a new design for the perimeter style, aluminium chassis that was thinner in width than past models, improving rider comfort and control. The 2013 model is only mildly tuned, more in concert with the PSF than anything else. To suit different preferences in riding position, the KX450F features adjustable handlebar and footpeg mounts. The handlebars features a total adjustment range of 35mm through the upper triple clamp, which enables the handlebars to be positioned 25mm forward, 15mm forward or 10mm backward, in addition to the standard position. Footpegs can be lowered 5mm. Doesn't sound like much, but it can make all the difference for some riders in lowering their centre of gravity.
A flatter overall shape for the seat and tank allows for easier, more comfortable adjustments in riding position, aided by smaller engine shrouds and side covers. The seat features a grippy top section and smooth sides for best possible comfort and mobility. For shorter riders, an optional rear suspension tie rod can lower the standard 955mm seat height by 4mm. Handlebar grips are 10mm longer, with the extra length added inboard, so the 'bars themselves aren't any longer.
Appearance-wise, the 2013 KX450F features a new design for the front mudguard and race plate, while the rear guard is finished in white, as per the factory racers. Graphics have been updated in the style of the US factory race bikes, with other factory-inspired touches including the black anodised rims, and blue anodised parts like the fork caps, rear shock adjusters, oil cap and generator cover.
All up, the 2013 KX450F ticks a lot of boxes for the serious racer, thanks to its widely-adjustable suspension and electronics. Initial reviews and first tests have been positive concerning, especially in the US, where the KX450F has a proven race-winning pedigree. Any local rider looking for a premier class motocross machine would do themselves no harm in putting the 2013 KX450F high on their shopping list.
SPECIFICATIONS - 2013 Kawasaki KX450F
Engine: 449cc DOHC 4-valve 4-stroke single-cylinder
Bore/Stroke: 96 x 62.1mm
Compression: 12.5:1
Power/Torque: N/A
Fuel System: Electronic fuel injection w/Keihin 43mm throttle body
Starting System: Kick
Cooling System: Liquid
Electrical System: 12 volt
Transmission/Drive: 5 speed foot change manual/chain drive
Front Suspension: 48mm Kayaba USD 'pneumatic spring' telescopic forks
22-way compression, 20-way rebound damping adjustment
Rear Suspension: Uni-trak swingarm rear with adjustable preload
33-way compression, 22-way rebound damping adjustment
Front Brake: 250mm ventilated petal disc w/2-piston caliper
Rear Brake: 240mm ventilated petal disc w/single piston caliper
Front Tyre: 80/100-21 57M
Rear Tyre: 120/80-19 63M
Weight: 112.5kg
Seat Height: 955mm
Ground clearance: 330mm
Fuel Capacity: 6.2 ltr
Top Speed: N/A
TRIVIA
Australian-delivered KX450Fs feature a greater overlap between the baffle pipe and tail pipe, to reduce the risk of failure when the parts expand due to heat.
An optional feature for the KX450F is a KX Fi calibration kit. This kit contains Kawasaki KX Racing software, ECU controller, mounting equipment, dampers and a USB cable to hook up to your PC or laptop. The kit enables users to adjust all three of the pre-programmed engine maps, adds an additional seven pre-set maps, and allows for up to six hours of data logging.
Kawasaki's KX 450F has enjoyed its best and most recent success in the USA, where it has won the 2011 AMA Motocross Championship, as well as the 2011 and 2012 AMA Supercross Championships. Ryan Villopoto was the rider for all three titles. Villopoto has been on a Kawasaki KX450F since his first year in the AMA Supercross series in 2009.
