What Hath Thou Wrought?
Although the new ZX-6R doesn't seem any smaller than its predecessor when you initially sit on it-the flared top of the fuel tank and the angular fairing give a false impression of size-that changes quickly when you first set your feet on the pegs and notice the narrower midsection, shorter reach to the bars, and shorter seat. There's more of a compact feel to the new 6R, even though the overall dimensions are basically the same.
That feeling is accentuated the moment you flick the Kawasaki into a turn. Whether through the more centralized mass (the engine is actually raised on the countershaft axis 4.6 degrees to reduce the polar moment of inertia) or due to the sharper steering numbers (24 degrees rake/103mm trail from 25.1 degrees/110mm), the new 6R is definitely easier to bend into a turn, requiring less effort in all aspects of steering. This was especially noticeable in Autopolis' many switchback sections that require pulling the bike from full lean on one side to the other; while the previous generation 6R was by no means truckish in this regard, the '09 Ninja has a more lithe feel that translates to quicker transitions with less effort. Granted, the ZX-6Rs we rode at Autopolis were all equipped with Bridgestone BT-003 DOT racing rubber that surely contributed to the more agile steering, but the difference was too great to be attributed to just the tires.
Thankfully that sharper and quicker steering hasn't come at the expense of stability. Even though Autopolis' pavement is a literal billiard table compared to 99 percent of American racing circuits, there are still plenty of fast sections that test a bike's ability to maintain composure while accelerating hard over bumps at moderate lean angles. The Kawasaki never felt like it was coming unglued at any time, even with initial suspension settings that were a bit too soft in the rear. We never felt the need to tighten up the Ohlins steering damper (which is actually a good thing, considering that even when cranked up to maximum, the OEM-spec Ohlins' overall damping rate is fairly light).
We're not sure if the new Showa BPF inverted fork played a role in that stability, but there was no doubt of the fork's aptitude at handling any situation we were able to put it through at Autopolis-ditto for the rear shock. We must admit, however, that we didn't notice the same difference in performance that we've experienced when switching to aftermarket fork cartridge kits on other bikes, although it should be pointed out that the Japanese circuit has very little of the pavement imperfections that plague most of the American racetracks we test at. With fewer and less harsh corner entry and midcorner bumps to really expose any high-speed damping deficiencies, it was difficult to discern any real improvement with the BPF, so we'll have to reserve judgment until we get a production model onto our less-than-perfect tarmac.
With its near-3000 feet altitude, the thin air of the mountain highlands where the Autopolis circuit is nestled tends to rob engine power, but even accounting for that factor, it was immediately apparent that the new ZX-6R powerplant is a major improvement over the old unit (even with the jumper wire mod to access the Euro engine map). The huge midrange hole that afflicted the previous model has been filled in nicely and then some, meaning that many tighter sections of the Autopolis circuit could be taken in third gear to maintain momentum, something that the old 6R could only dream of. That stronger midrange transcends into an even stouter top-end that not only towers over the old strangled U.S. version by a claimed (and astounding) eight horsepower, but the new U.S. version now only trails the Euro-spec '09 Ninja by less than two horsepower at peak.
This diagram illustrates the...
This diagram illustrates the concept employed by the Kawasaki's "multi-boring thread insert" plain bearings. By changing the depth of the microscopic oil grooves across the bearings' face, oil is captured more efficiently resulting in a stronger oil film and less friction.
This diagram depicts the internal...
This diagram depicts the internal differences between a standard cartridge fork (left) and the Showa BPF fork (right). Because the BPF basically converts the lower fork tube into the "cartridge", it doesn't need many of the parts necessary in a conventional cartridge fork, such as the internal cylinder and the sub piston, saving weight. Also, because spring preload is now located on the bottom, there no longer needs to be a sleeve running up to the top fork cap. The comparatively huge main piston in the BPF allows substantially more fluid flow through the damping orifices (which can now both be positioned in the main piston instead of separately), which drops fluid pressure and dramatically reduces the tendency for cavitation that causes irregular damping issues.
This computer-generated image...
This computer-generated image shows how Kawasaki engineers altered the new ZX-6R's chassis rigidity for improved rider feedback. The gold-colored front portion shows how the upper engine mounts are now connected directly to the steering head, increasing rigidity in that area. The blue sections represent the larger pressed beam sections that actually provide more lateral flex for better feedback when leaned over. The green portion shows the rear engine mounts that are now part of a one-piece cast component for more rigidity over the previous tabs welded onto an aluminum pipe.