CarBrandLogos archive · Kawasaki · 1972

KawasakiZ1

Nine hundred cubic centimetres of four-stroke four, built because Honda got there first.

Photo: Manju · CC BY-SA 3.0

The story

A defining chapter in Kawasaki history.

Explore the ideas, engineering and context that shaped the Kawasaki Z1, then continue into its specifications and place in the marque's lineage.

Origins

Kawasaki had been developing a 750cc four-cylinder four-stroke — internally "New York Steak" — when Honda unveiled the CB750 in 1968. The project was effectively dead as conceived: releasing a comparable machine two years later would have achieved nothing. Rather than abandon it, Kawasaki went bigger, and used the extra time to engineer something meaningfully more advanced.

1974 Kawasaki 900 Z1 · Chuck Schultz · CC BY-SA 2.0

Design and engineering

The Z1 arrived in 1972 with 903cc, double overhead camshafts, two valves per cylinder and a five-speed gearbox. Where the CB750 had a single camshaft, the Z1 had two, and it made appreciably more power — enough to be the fastest production motorcycle you could buy. Its styling, from Kawasaki's own studio, gave it a teardrop tank, a four-pipe exhaust and a ducktail seat unit, a shape the company's retro models have referenced ever since.

In production

Durability was the other priority, since high-mileage weakness had been the CB750's soft spot. Before launch, Kawasaki took Z1s to Daytona and ran them at sustained high speed for distance records, and the bottom end proved strong enough that the engine became a default choice for drag racers and for the endurance teams who went on to build the first true superbikes. Tuners could take it well past 1,000cc without redesigning it.

Legacy

Around 85,000 were built to 1975, after which the Z900 and then the Z1000 continued the line, growing in capacity and weight through the decade, and the architecture underpinned Kawasaki's big four-strokes into the 1980s. Its influence spread well beyond the company: the Z1 established that a Japanese manufacturer would keep escalating displacement and power, and Honda, Suzuki and Yamaha all answered with four-cylinder machines of their own. The horsepower contest of the following forty years starts here.

Chapter 5

Original Z1s, particularly the first-year cars in candy brown and orange, are now among the most valuable Japanese motorcycles, and Kawasaki has since built modern retros — the Z900RS chief among them — that copy the tank shape and the colours quite deliberately.

At a glance