After four years of offering their 636 cc ZX-6R for street use and an entirely separate 599 cc ZX-6RR for displacement-restricted racing classes, Kawasaki offered only one ZX-6R for 2007, and it displaced 599 cc. Previous years of the ZX-6R's engines were all built from the same basic design, but the all-new engine for 2007 was redesigned from the crankcase up. In following with what their competitors had already been doing, Kawasaki's new engine featured a stacked gear arrangement in which the crankshaft, primary drive and countershaft are placed in a triangular format for a shorter, more compact powerplantPP Tuning performance parts for Kawasaki Ninja ZX-6R (2007) rearsets, adjustable brake and clutch levers, clip-on handlebars, protectors etc. are produced from highly resistant materials. This ensures their longevity.