It's no secret that Kawasaki's ZX-6R has been taking a pummeling from the competition for the past couple of years. Although the chassis is one of the better-handling units available, the engine was a little short on steam, a critical deficiency in the ultra-competitive 600 class. And for a manufacturer that prides itself on a reputation for power, it was a situation that bordered on embarrassment.
With the now-standard two-year development window for the ZX-6R approaching in '09, you just knew that Team Green wasn't going to mess around with the next generation 600. And by all appearances, it looks like the boys at Honda and Yamaha better sharpen their swords-the new ZX-6R is heavily redesigned and looking to take names.
A Mini ZX-10R?
Although the physical resemblance to its ZX-10R brother is unmistakable, there's been far more changes than just new bodywork. Both engine and chassis of the new ZX-6R have undergone substantial revamps.
While the 599cc powerplant's bore and stroke dimensions remain unchanged, a plethora of internal improvements have been wrought with the intent of reducing weight and friction while increasing efficiency for more power. For instance, the crankshaft main bearing inserts have been changed to a new material that is claimed to significantly reduce friction by propagating a smoother and stronger oil layer between the journal and bearing surface. The ventilation holes between each cylinder cavity in the crankcase have been revised, and the cam chain guide has been redesigned to a straighter path for less friction. Other changes down below include narrower gears (reducing overall weight by more than 0.5 pounds) with revamped engagement dogs in the cassette transmission, and the oil pump gears are made from a different material to save weight. An additional 610 grams were cut by going to magnesium engine covers.
The cylinder head has undergone major revisions despite retaining the same size valves. The intake and exhaust ports have been reshaped, with a noticeably increased volume near the valve seats contributing to better cylinder filling in conjunction with the ram-air induction. The camshafts have new profiles to enhance low-end and midrange power, while their new chrome-moly steel construction helps drop nearly one pound of weight. New pistons feature different skirt profiles with moly coating (less friction again), with new crown profiles for better combustion efficiency while compression ratio remains the same; even the piston rings have been revamped to provide less tension (for-you guessed it-less friction). The stick coils in the spark plug caps now feature rare-earth magnets that help boost coil output by 12 percent for increased combustion efficiency.
The electronic fuel injection system has also undergone some changes, although it retains the same throttle body size, dual injectors per cylinder and injector angle as before. The previous oval throttle bodies have been swapped for a setup featuring round bores with oval intake trumpets, and the distance between the primary and secondary throttle plates has been increased by 10mm to improve throttle response in conjunction with the redesigned intake ports. Because the airbox lid is slightly shallower to accommodate the reshaped fuel tank, the secondary injectors are now shrouded to protect them from the turbulence that is present in that lower position near the intake funnels.
The intake funnels themselves feature an innovative "sub-throttle port" design intended to improve both midrange and top-end power in a manner similar to variable height intake funnels but without the weight and complexity. Each funnel has a shorter sub-funnel molded into its forward-facing portion; while the taller main portion works with the longer intake resonant pulses at midrange rpm to improve power in that area, at higher rpm the shorter sub funnel helps enhance flow by not only matching the intake resonance better but also provides a straighter path for the incoming airflow from the redesigned ram-air induction system.
That ram-air system has been slightly changed with a shorter but incrementally (2mm wider) larger cross-section that increases overall airbox pressure at speed. The duct itself has been reinforced so that it now fully supports the instrument panel and mirrors, eliminating bracketry and weight.
Down below, an all-new titanium exhaust system replaces the old underseat setup with an underengine unit utilizing the same type of pre-chamber as the ZX-10R's to cut noise and reduce muffler volume. A single catalyzer featuring a higher-flowing 300-cell design keeps unwanted emissions in check.
On the chassis side, the new ZX-6R's twin-spar aluminum frame underwent subtle tweaks to the cast and extruded members (such as a switch from convex to concave cross-section in a similar fashion to the ZX-10R) to tune chassis rigidity for better feedback. In order to reduce the bike's polar moment of inertia (for quicker handling), the engine is actually rotated upward on the countershaft axis 4.6 degrees, moving the front portion up 16mm; the steering head pipe was moved up 10mm to make room. Rake and trail get quickened up as well, moving from 25.1 degrees/110mm to 24.3 degrees/104mm.
A new Showa BPF (Big Piston Fork) inverted fork is featured up front. Interestingly, instead of the usual internal damping cartridges that utilize 20-25mm pistons found on conventional inverted forks, the Showa BPF unit basically does away with the internal cartridge and transforms the lower fork tube itself into the "cartridge". This enables the use of a comparatively huge 37mm piston that significantly increases the amount of oil that can flow through the damping orifices, which in turn reduces the possibility of cavitation that can cause irregular damping. The large piston contains both rebound and compression damping mechanisms. The fork spring is still located on the bottom; but, the adjusters for both rebound and compression are now positioned on the fork cap, while the spring preload adjuster is situated on the bottom of the fork leg where the compression damping adjuster used to be. The rear shock remains unchanged, but gains a "pillow ball" upper mount that spreads suspension loads better.
The switch to an underengine exhaust meant the rear sub frame could be made lighter, so the new section is now made from two precision die-cast pieces. A side benefit to the new rear sub frame is a 10mm reduction in seat height. The '09 ZX-6R gains new bodywork styled to strikingly resemble its ZX-10R big brother, as well as a similarly styled instrument panel featuring an analog tachometer with inset LCD panel; special UV-blocking glass is claimed to make the LCD panel easier to read at a glance.
Unfortunately other important info such as weight and list price weren't available at press time. However, Kawasaki reps state that the target weight for the new ZX-6R was the Honda CBR600RR, the current flyweight of the class, and if all the upgrades hit their mark, you can bet the new Kawasaki will shake up the middleweight category. And it's highly unlikely that the MSRP will be set well outside current 600-class norms.
We'll have ridden the new ZX-6R by the time you read this, so expect a full report in an upcoming issue.