Classic Motorcycle Build

GPz 750 Turbo

Article by Mark Trotta

After three years of development, Kawasaki released the GPz-750 turbo in 1984, the last of the big-four Japanese motorcycle companies to offer a regular production turbo bike.

Kawasaki GPz-750 turbo bike history

Although looking identical to the naturally-aspirated GPz-750, the turbocharged 750 was indeed a different animal. Upgrades were made in nearly every category to handle the turbo motor's 112 horsepower.

Turbo Bike History

In 1980, Kawasaki pioneered the first fuel-injected bike with the KZ1000G, based on their Z1 900cc engine, and housed in the LTD cruiser chassis. Honda took the next major step in innovation, with the first fuel-injected and turbocharged motorcycle, the CX500TC. Released in 1982, it out-performed Honda's own CB900F while returning better fuel economy than the base-model CX500. The Yamaha Seca Turbo was the second regular production turbo bike.


Fuel Injection vs Carburetion

In the early eighties, automobile manufacturers were grappling with fuel-injection to comply with stricter emission regulations and rising gas prices. For motorcycle manufacturers, it was just another way to make more power.

Unlike carburetors, fuel-injected systems always deliver the correct fuel mixture at all times - cold or hot, high revs or low. In addition, airflow does not have to pass through a venturi to provide the air/fuel mixture, so the throttle-plate diameter can be larger. By giving an engine more air, horsepower potential increases.

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Kawasaki GPz-750 Turbo (1984-1985)

Based on Kawasaki's existing inline-four engine, the GPZ's turbocharger was placed in front of the cylinders and close to the exhaust ports, helping reduce turbo-lag. The front down-tubes and double-steel cradle made the frame more rigid and helped protect the turbo unit in the event of a crash.

A steep 28-degree fork angle and short 1490mm wheelbase gave the GPZ750T quick and precise steering. Cornering clearance was good, and the Uni-Trac air-adjustable single-shock rear suspension with aluminum swing arm worked well. But the reason why the 750-turbo out-performed all other production turbo-bikes was its induction system.

Kawasaki GPz-750 turbo engine

For the 750-turbo, Kawasaki developed a digital fuel-injection system. Minor adjustments were made continuously, via various sensors, producing a smooth and responsive power curve. Stored trouble codes indicating malfunctions could be recalled by a technician.

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Stock performance of this bike was on a par with the GPz-1100. Quarter-mile times were low 11 seconds at 125-mph, and recorded top speeds at over 145-mph. In 1985, a 750-turbo piloted by racer Jay Gleason ran a 10.71 second quarter-mile time, breaking Gleason's own fastest production motorcycle record of 10.84 seconds, set in 1983 on a Honda V65 Magna.

The 750-turbo record would stand for little more than a year, when it was Gleason again breaking his own record on a Yamaha V-MAX, clocking a 9.53 second quarter-mile run.

Assembled In America

It was during this time the U.S. government, in an effort to help the Harley-Davidson Motor Company keep afloat and save American jobs, levied an import tax on imported bikes over 700cc. Although the 750-turbo was manufactured in Japan, Kawasaki got around the tariff by shipping the bikes disassembled to their Nebraska, U.S. plant and having the bikes reassembled there.

Kawasaki GPz-750 turbo bike history

As more power was coaxed out of naturally-aspirated engines, the more expensive and complex turbos fell out of favor. 1985 would be the last year a production turbocharged motorcycle was offered for sale in the US. Kawasaki produced around 5500 turbo-bikes for the 1984 model-year and approximately 2500 in 1985.


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