The ZX-RR's unorthodox rear...
The ZX-RR's unorthodox rear shock setup positions the unit upside-down, which is why the shock reservoir that usually protrudes from this area isn't visible. Although this helps keep the bulk nearer the bike's center of mass, Kawasaki MotoGP race director Ichiro Yoda admits it was done mostly for ease of spring and linkage changes-the shock can simply be dropped down instead of having to be maneuvered out from between the swingarm and tailsection.
AC: Was the unorthodox rear shock mount on the new 800cc Kawasaki also designed to improve mass centralization?
IY: For sure. One of the reasons we run an unorthodox mount for the rear shock by effectively running it upside down in the chassis is that it places the majority of the weight closer to the central mass of the engine. But the main reason for using this method of mounting the rear shock was for ease of maintenance. Running the inverted shock makes changing the spring and altering suspension settings much easier and much quicker to do when the pressure is on during practice and qualifying.
AC: How many parts does the new 800cc ZX-RR have in common with the old 990?
IY: The 800cc machine is an evolution of the 990cc bike, so we have taken what we learned during the past four years and incorporated those lessons into the design of the new machine. Yes, there are some parts that remain from the 990, such as the running gear and bodywork, but the major components like the engine and chassis are all new, although the bore-to-stroke ratio of the engine did not change so much. This is a motorcycle, not a car, so we do not use an extreme short stroke. The chassis is very similar to the final 990 version, although we changed dimensions slightly, and also the center of gravity is altered.
The mass centralization philosophy...
The mass centralization philosophy of the ZX-RR's design is obvious without bodywork. Note the pneumatic valve componentry on the side of the cylinder and head assembly, as well as the long length of the 4-into-2 collectors leading to the single megaphone, indicating Kawasaki's continued use of the long-bang firing order (however, during '08 preseason testing Kawasaki was apparently experimenting with a screamer-firing-order engine, with traction control used to tame its aggressive power off the corners).
But we made many experiments with different stiffness of the chassis and swingarm, especially in relation to each other. The 990cc bikes had so much power that a lot of our development time was spent trying to counter the tendency to lose grip at the rear under acceleration. The bigger bike could feel quite nervous to the rider on the throttle, and when it did lose rear traction it did so suddenly. The characteristics of the 800cc ZX-RR are that it's easier to control on the throttle, and the transition between grip and no grip is both smoother and more predictable. The engine is the input for the whole system. Because the engine is smoother with the 800cc bike it means the whole system is more stable, so now we can experiment with chassis and swingarm stiffness to get ideal handling characteristics.
AC: Valentino Rossi is reported as saying that you need a V-four engine to win in MotoGP. So is Kawasaki working on such an engine for the future?
IY: This is stupid! Each kind of configuration has its own advantages, and Ducati is not winning just because it is a V-four! Kawasaki has very much experience of inline-four-cylinder engineering, and we will continue in this direction, not produce our own Ducati copy. We believe the handling advantage of our inline engine comes from a more compact mass and this makes a better package compared to a V-four-also because a V-four is more difficult to fit in a chassis, and maintenance is more complicated, too. Maybe for Honda this is OK, because they have a lot of V-four experience. But for Kawasaki this is not the case, so we will continue to follow our experience with the inline layout.