Moto History 101: The Kawasaki Square-Four 750

Motorcycle manufacturers love bragging rights. Whether that be top horsepower or reliability, OEMs relish the opportunity to separate from the pack. For Kawasaki, top speed was the ultimate bragging right in the late ‘60s and early ‘70s. That's why the brand was crestfallen when Honda’s CB750 topped the two-stroke, 500cc Mach 3 in 1969.

To regain its speed crown, Kawi unleashed the Mach 4 in 1971. The two-stroke, 750cc, inline-triple reached 126 mph and reclaimed the title for Team Green. The brand increased its advantage when it released the Z1 in 1972. This time, Kawasaki flexed its four-stroke muscles with a 900cc inline-four capable of a 130-mph top speed.

Despite those achievements, Kawasaki wasn’t going to rest on its laurels. Led by the “Father of the Mach” Hiroyuki Matsumoto, the team of engineers and designers rolled up their sleeves and started work on the fabled Square-Four 750. Labeled with the code name Steak Tartare, the project aimed for raw power and outright speed. Those weren’t the only objectives, however.

Gallery: 1971 Kawasaki Square-Four 750 Project

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Like a great dish, the team aimed to create a well-rounded experience with liquid-cooling and a compact square-four layout. Matsumoto and company decided to unify the right cylinders (front and rear) and the left cylinders (front and rear) with a twin carburetor connecting both respective halves. The team even developed a fuel injection for the square-four engine as an alternative fuel delivery system. To prevent power loss, a two-into-one exhaust system was bolted to the right and left exhaust ports.

Though Kawasaki spent years of research and development on the square-four platform, U.S. emissions regulations foiled the muscle bike’s production prospects. Team Matsumoto was, unfortunately, forced to abandon the project in 1973. This was particularly cruel, as Kawasaki was far along in the development process. Gauges, lights, and even an electric starter motor were equipped by the time Team Green pulled the plug. While the Square-Four 750 wouldn’t add to Kawasaki’s bragging rights at the time, it never dampened the brand’s spirit. That fact is evident with today’s H2 lineup.

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