KAWASAKI KZ500/550 and the KAWASAKI GPz550

Kawasaki Z500,Z550 and GPz550

"Announced in 1978, the Z500 was directly related to the Z650. The plain bearing four now had a hyvo cam-chain and six speed gearbox, and displaced 497cc through downsized, 55 x 52.4mm dimensions. In most other respects the whole bike was like the 650, but a bit smaller and lighter. Sitting on a 55 inch wheelbase and wheighing about 430lb ready to ride, it was an inch or two shorter and wheighed 60lb less than big bro.

From the start the 500 had three disc brakes and cast wheels. Styling was best described as "understated", which is a kind of way of saying fairly bland and unadventurous. Still, with 52bhp at 9000rpm it went quite well, in a characteristically revvy Kawasaki way.

BIKE magazines' reporter suggested that the 500 would fill the gap left by the much loved Honda CB400/4, but that didn't happen. It was too expensive for one thing. Part of the little Hondas' secret was a bargain-basement price (less than 900Pds when replaced by the 400T Dream twin in 1978). Making due allowance for inflation, the Z500 really occupied a different sector of the market. If your paying 1,250Pds, why not spend 400Pds more for a Z650, which wouldn't be too financially painful when spread over a three year HP agreement?

A year later, the engine grew another 3mm in the bore to become the Z550 (that's what it said on the side, although elsewhere it was KZ550, because Kawasaki seemed to have adopted the American model designation system). The standard roadster was joined by the LTD, with the expected fat 130/90-16 rear wheel, stepped seat, high handlebars, abbreviated mudguards and suspect handling.

1981 was the year Kawasaki pulled a rabbit out of their hat, by launching the GPz series of sportbikes. (Incidentally the "z" was supposed to be lower case in the early days, and only started to become a "Z" in 1983, when the GPZ900R arrived on the scene.) Three GPz models were unveiled, having been in development since 1978. At entry level the target for the GPz550 was 120 mph and a 13 second standing quarter-mile. To boost power from 54bhp to 58bhp at 9000rpm, the compression was raised to 10:1 and the cams changed to give 0.7mm more valve lift ans 22 degrees longer duration. In real life the tuned engine gave about 15% more power than the ordinary four.

Tested by the American magazine MOTORCYCLIST, the result was a 12.5 7 second/104mph standing quarter, which seemed incredible. Or completely unbelievable, bearing in mind the claimed horsepower and 200kg weight. British road tests achieved less spectacular results, as usual, but the GPz550 was still substantially faster than the Z550, and effectively offered the same performance as the original Z650.
Nothing had changed on the chassis front. The forks were now air-assisted, a good-in-theory, bad in practice idea, because the legs weren't linked and the volume of air inside was so small that it was difficult to set the pressure at one side, let alone balance the two. "Infinite adjustability", Kawasaki claimed. They weren't joking.

Style was the GPzs' secret of success. Bright red paintwork, subtle graphics, black engine and exhausts, with polished alloy hightlites on the wheel rims and cylinder head. Everybody seemed to like the new look, and it was instantly identifiable, which is a marketing dream."

Classic Japanese Motorcycle Guide by ROD KER

Kawasaki Z500/Z550

The Kawasaki Z500/Z550 series began with the 1979 Z500, a scaled-down version of the 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 motorcycle. Contents [hide] 1 Z500/Z550 (KZ550) 2 ZX550 (GPz550) 3 Z400 J Series J1, J2, J3 4 References [edit]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 disc brake) and a drum brake in the rear, with a conventional swingarm using twin shock absorbers. Later models (1982-1983) had improved brakes (twin discs in the front, with a single disc in the rear). The original Z500 (1979-1980) differed from the early Z400/Z550 models in having twin front and single rear discs.


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 carburetors; later models had CV carbs. A monoshock rear swingarm was introduced in 1982 on the model Gpz550H.[3] In 1984 the GPz was offered in silver with red and blue stripes as well as the introductory red. Other styling changes included a larger fairing and a new rear suspension.[2] The model was later substantially revised to the Gpz550A1 which had updated bodywork and revised valve timing increasing power to 68bhp.

Z400 J Series J1, J2, J3

Introduced in the UK in 1980 as the J1 version, their styling and spec was aimed at the sports touring market and as a competition against the Honda CB400/4 and 550/4 series of successful UJM (universal Japanese motor) middleweights. The 400 was almost the same in specs as the Z500 model but differed in that it had a rear drum brake instead of a disc. The J2 was fitted with air assisted forks, adjustable damping rear twin shocks, tubeless tyres in cast 7 spoke wheels, grab rail and different tank/seat cowl striping The J 3 version was offered was Megaphone shortie silencers and chromed tops on the twin shocks. In 1983 the Z400 was altered significantly and the engine was heavily reworked resulting in the ZR 400.