Kawasaki Z500/Z550

This series began with the 1979 Z500, a scaled-down version of the legendary Kawasaki Z1R. It used a double-cradle steel (Norton featherbed-style) frame with a transverse-mounted air-cooled 4-cylinder DOHC(Double Over Head Cam) engine--a classic universal Japanese motorycle.

Z500/Z550 (KZ550) - This was the first of the line, with a 500cc DOHC engine, later bored out to 553cc's and also available as the 398cc Z400J (identical to the Z550). Early Z550 models (1980-1981) had a double disk brake in the front (The US model KZ550 had a single disk brake) and a drum brake in the rear, with a conventional swingarm using twin shock absorbers. Later models (1982-1983) had improved brakes (twin disks in the front, with a single disk in the rear). The original Z500 (1979-1980) differed from the early Z400/Z550 models in having twin front and single rear disks.

ZX550 (GPz550) - Introduced in 1981, this was a slightly more aggressive version, with improved brakes, larger valves, more aggressive tuning, and a bikini fairing. The first model, the Gpz550D had slide carburettors, later models had CV carbs. A monoshock rear swingarm was introduced in 1982 on the model Gpz550H. The model was later substantially revised to the Gpz550A1 which had updated bodywork and revised valve timing increasing power to 68bhp.

Living with the Z500/Z550 These make excellent city bikes, very easy to manage at parking speeds and very agile in urban traffic. They have safe, neutral, tossable handling and a flexible engine, making them fun to drive without being too intimidating for first-time riders. These machines are also very easy to work on, with ample engine access, a simple electrical system, and a very reliable drivetrain.

Earlier models suffered from inadequate brakes and bad clutch cable routing; these issues were resolved with the 1981-on models, which also featured a simplified clutch cable and electronic ignition. Despite these constraints the original Z500 model was a road-going race bike with a free revving engine, triple disks and its own race series. Britain's best known formula one champion Damon Hill began his racing career riding a Z500 in competition.

The Z500/Z400/Z550/GPZ550 series developed into the GT550 shaft drive in 1983 and eventually the 1991-on Zephyr (ZR550) models. With a twenty two year model run in various incarnations they have gained a reputation for reliability and longevity reinforced by numerous examples of GT550 courier bikes covering in excess of a quarter of a million miles despatching in London.