Kawasaki Injects excitement
By TMX Archives on 18th Jun 08
KAWASAKI will deliver not one, but two, virtually brand-new four-stroke machines for 2009. That is the news announced by the Japanese giant as it unveiled details of it's 2009 range to the worlds press early this week, and the big story coming from the green corner is that the formidable KX450F will arrive equipped with Electronic Fuel Injection (EFI), following the trend set by Suzuki's ground-breaking RM-Z450 this season.
It is not just a case of Kawasaki bolting on an injector system either as just three years after the launch of the KX450F, and the totally new KX250F, Kawasaki has indulged in massive changes to both the engine and chassis' of both machines, particularly the much respected uni-trak rear linkage system, that will see them arrive radically different to their predecessors.
Of course it is the EFI system, which of course Kawasaki feels improves throttle responsive and all round engine performance, that will take the headlines but the incredibly popular and successful KX450F gets a huge overhaul along with the addition of the injector system, including a new more compact head with revised exhaust and intake ports, a new piston with up the compression ratio from 12.0 to 12.5 for increased low-to-mid power, and new crankshaft which promotes an improved response and smoother power.
Minor detail changes are dotted about across the engine block, but other key components such as the gearbox appear to remain unchanged.
The chassis on both the 450 and 250 are radically different, however, with the changes made to the KX450F aimed at promoting a lighter, slimmer package with superior all-round handling, but specifically improved rear-wheel traction and control.
As a result the main frame rails and headstock have been shaved down to reduce weight and reduce bike width by 6mm, and a new swingarm with reduced weight and improved rigidity is fitted.
It is the developments made to the Uni-trak linkage system which are most significant though with the swingarm pivot now positioned higher on the frame and the revised linkage now mounted below the swingarm to produce and longer stroke and more precise suspension tuning. The end result of the changes says Kawasaki is vastly improved rear-wheel traction. The rear-shock itself doesn't go untouched and gets a new 50mm piston, up from 46mm, for a plusher ride at the bottom-end of the stroke in particular.
Up front the bike gets steeper offset of 23mm to promote quicker turning and increased front-end grip while new outer fork tubes upper triple-clamp are also used to provide better rigidity.
In keeping with the new lighter, slimmer theme the bodywork on the KX450F, and also the smaller KX250F, has also been revised with the seat been shaved down in width along with the new rad shrouds and side-panels, while wider foot-pegs have been fitted to give the rider better control.
The KX250F also shares the new swingarm and linkage changes as its bigger brother, along with the larger shock piston, but the improvements the Kawasaki engineers were looking for in terms of the chassis were for increased sharpness of handling, especially in tight corners.
As a result the KX250F frame features new main frame rails and bracing around the fuel tank, the upper engine mounts have been repositioned, and a new downtube has been designed. The front-end has also been tucked in to accompany these changes and further promote faster handling, and the bike also benefits from new twin-chamber Showa forks.
Already the owner of a world and AMA championship winning motor, the KX250F gets a very comprehensive makeover too to further boost output and reliability with a new cylinder head with specially coated intake ports for better intake efficiency and power topping the list. Also included is a new water jacket, a new tapered titanium exhaust for increased throttle response and power at the top and bottom of the rev-range, a revised crank web for smoother power delivery and increased mid-top power, a revised ignition timing, and increased radiator capacity for better cooling. A new shifter mechanism also promotes smoother shifting.
All in all Kawasaki really has done some serious work to its two flagship off-road machines and T+MX News looks forward to seeing how the exciting new KX450F in particular shapes up when the bikes are released later in the year.