The Z1 Kawasaki was a motorcycle introduced in 1972 by Kawasaki Heavy Industries. It has sometimes been described as the world's first superbike. The Z1, along with Honda's CB750 from 1969, introduced the four-cylinder, across the frame, disc-braked layout to a wider public. The Z1 was groundbreaking in that it combined many different elements which previous motorcycles had used into one performance package.
The Z1 Kawasaki was developed in strict secrecy under the project name "New York Steak". Some years previously, Kawasaki, already an established manufacturer of two-stroke motorcycles, decided to make a 750cc 4-cylinder 4-stroke sports motorcycle; they were beaten to the market place by the Honda CB750. Apparently, the bosses at Kawasaki disapproved and ordered their designers to come up with something better.[1]
Stone was an Australian film that featured several Z1s ridden by a post-Vietnam veteran's outlaw biker gang.
The basic design of the Z1 remained relatively unchanged until 1975, when the 903cc "Z1-B" was introduced, with changes including power output, improved suspension, a stiffer frame, deleted automatic chain oiler, revised styling (essentially paint scheme and side cover nomenclature), and improved braking.