The Kawasaki Ninja ZX-6R is a Kawasaki middleweight sport bike. It was introduced in 1995 and has been constantly updated throughout the years in response to new products from Honda, Suzuki, and Yamaha. The ZX series is what was known as the Ninja line of Kawasaki motorcycles in the 1980s and still carries the moniker in North America today.
When Kawasaki introduced the ZX-6R in 1995, it was the industry's first middleweight sport bike with an aluminum frame. It had a dry weight of 401.2 lb (182.0 kg), wet weight of 454 lb (206 kg), and was capable of accelerating 0-60 mph (97 km/h) in only 3.6 seconds.
1997 Kawasaki Ninja ZX-6R
With competition from Honda's CBR600F4i, Suzuki's GSX-R600, and Yamaha's YZF-R6 getting more aggressive, Kawasaki decided to make an unusual move for the 2002 model year. They increased the capacity of the traditional 600 cc (37 cu in) motor to 636 cc (38.8 cu in). For riders who needed bikes for displacement-restricted racing, Kawasaki also made available a limited production 599 cc (36.6 cu in) version called the Ninja ZX-6RR, but the 636 cc (38.8 cu in) ZX-6R would be their main mass production middleweight sport bike.
2002 Kawasaki Ninja ZX-6R
2003 brought many new changes to the ZX-6R, or ZX636 as it is often referred. The engine was now fuel injected and engine speed was raised around 500 rpm which resulted in a slight gain in power. Radial-mounted 4-piston brakes replaced the previous 6-piston brakes and the front forks were now inverted. Chassis improvements resulted in higher rigidity and less weight. An all digital instrument panel was also introduced and a larger ram air inlet moved to the center over the headlight, running through the headstock. The bike carried over to the 2004 model year with just color scheme changes. The ZX-6RR won the Supersport category award for Masterbike 2004 and placed 3rd overall. MSRP for the 2003/2004 models was $7999 USD.
2005 Kawasaki Ninja ZX-6R
In 2005, Kawasaki again revamped the ZX-6R. Engine speed increased again by 1,000 rpm resulting in 105 hp (78 kW) at 12,250 rpm.  The frame and swingarm were updated, but the main changes from its predecessor lay in the design. The aluminum frame was now painted flat black, fairings were more round, and integrated turn signals were used (euro model). The exhaust was now centrically under the seat (a configuration commonly referred to as an undertail exhaust). Most of these changes were mirrored in the 599 cc ZX-6RR. For the second year in a row, the ZX-6RR again won the Supersport category award for Masterbike 2005 and placed 3rd overall. The bike carried over to the 2006 model year with minor suspension changes and new color schemes. The 2005/2006 ZX-6Rs had an increased MSRP of $8,699 USD.
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 offers only one ZX-6R for 2007, and it displaces 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 features a stacked gear arrangement in which the crankshaft, primary drive and countershaft are placed in a triangular format for a shorter, more compact powerplant. It's now about 40 mm smaller in both length and width, said to yield greater cornering clearance. By using a former 125 cc Grand Prix racer as the ZX-6R’s chief development rider, Tomomi Manako, Kawasaki claims a focus has been put on track usage. Frame, swingarm, suspension, brakes, and body are completely redesigned and the bike shares very few parts from the previous model. MSRP was increased to $8,999 USD and the ZX-6R expected to carry over to the 2008 model year with just color scheme changes.
All specifications are manufacturer claimed.