Kawasaki GPz 750 Turbo / ZX 750-E1


Make Model

 Kawasaki  GPz 750  Turbo / ZX750-E1


1983 - 85


Four stroke,  turbocharged, transverse  four cylinder, DOHC, 2 valves per cylinder


738 cc / 45.09 cu-in
Bore x Stroke
66 x 54 mm
Compression Ratio
Cooling System Air-cooled


Mikuni fuel injection


Staring Electric

Max Power

112 hp / 82.4 kW @ 9000 rpm

Max Torque

99.1Nm / 73.1ft-lb @ 6500 rpm

Transmission  /  Drive

5 Speed 
Final Drive Chain

Front Suspension

37mm air-adjustable forks, adjustable anti dive.
Front Wheel Travel 130 mm / 5.1 in

Rear Suspension

Kawasaki Uni-Trak air-adjustable single shock, adjustable for rebound damping.
Rear Wheel Travel 104 mm / 4.0 in

Front Brakes

2x 280mm discs

Rear Brakes

Single 270mm disc

Front Tyre

110/90 V18

Rear Tyre

130/80 V18
Dimensions Length 2,220 mm / 87 in
Width  740 mm / 29 in
Wheel base 1490 mm / 59 in
Seat Height 780 mm / 31 in

Dry Weight

 223 kg / 492 lbs
Wet Weight 241 kg / 531 lbs

Fuel Capacity 

18 Litres / 4.8 US gal

Standing ¼ Mile  

11.5 sec 

Top Speed

218.8 km/h / 136 mph

Kawasaki were the last of the four major Japanese manufacturers to release a turbo-charged motorcycle but were the only factory to achieve the ultimate turbo ambition - to transform a medium-sized motorcycle into something as quick as anything around. The Z750 is the world's fastest production turbo motorcycle - 112bhp at 9,000rpm, a top speed of 146mph and road-tearing acceleration that can cover the standing quarter mile in 10.9sec.

For many years, turbo-charged bikes had been the preserve of individual builders, tuners and drag racers, who adapted big Japanese four cylinder engines with bolt-on conversions for extra, high-speed thrills. Later Honda, Suzuki and Yamaha produced turbo bikes, all 650cc and all dismally received in the market. Kawasaki's 750 was bigger yet lighter than any and an instant, well-acclaimed success. The others have all been withdrawn,  and enhances yet further their reputation for building large, powerful, bulletproof engines.

On full boost, the Z750 Turbo shoots, shouts and screams speed.

Where Kawasaki significantly differed from the other manufacturers was in the design and location of their turbo-charger unit. They beefed up one of their existing inline four cylinder engines, the Z750, but instead of mounting the turbo behind the engine, Kawasaki put it up in front of the cylinders, very close to the exhaust ports. In a limited space of 7.5in, they managed to run four highly heat resistant steel pipes from the ports to a collector and thence to a tiny Hitachi turbo-charger. Such innovative positioning reduced turbo lag significantly.

 The result is instant response. Running a fairly modest 10.5psi of boost pressure the Z750 has excellent pick-up and strong acceleration anywhere above 5,000rpm when the turbo is spinning hard.

The turbo power does not bang in at a set rpm like many back street, bolt-on turbo bikes. From 5,000 to the 10,000rpm redline, there is plenty of boost and real poke, yet it is smoothly delivered. The turbo effect is unobtrusive. The acceleration is unforgettable.

In roll-on tests in high gears, the Kawasaki will annihilate much larger capacity bikes including its own big brother, the mighty GPz1000.

The smooth response and excellently rounded power curve are helped considerably by Kawasaki's digital fuel injection system. Kawasaki pioneered fuel injection on modern sports bikes and their computer-linked system, measuring and monitoring engine speed, throttle opening, intake pressure and engine/air temperature, ensures the Turbo runs at its best.

The rolling chassis is unremarkable but for the sleek, full fairing which features an integrated, aluminium frame member. This is a central section located between the frame's front down tubes which makes the double steel cradle more rigid, improving stability and protecting the turbo unit from crash damage. One notable detail can be found in the sealed, O-ring, final drive chain which is silicone lubricated and has special cut-outs in every other link to reduce weight and heat build-up.


Kawasaki ZX750E1 vs. Yamaha XJ650LJ

In life we’re faced with choices: republican or democrat, blond or brunette, paper or plastic? Shopping for a new motorcycle in the early 1980s, you also had to choose between normally aspirated or turbo models.

As the 1980s picked up steam, each of Japan’s Big Four (Honda, Kawasaki, Suzuki and Yamaha) offered up at least one turbocharged model based on a standard offering. The train of thought was simple: Combine a 650cc or 750cc engine with the power boost of a turbo and wham! — big power. For some shoppers, just the allure of turbo technology was reason enough to buy. And while each manufacturer (excepting Honda) used the same basic formula (inline-four engine + turbo = new model), each company’s creation was a bit different.

To get an idea of what the Turbo Wars netted, we pitted Kawasaki’s ZX750E1 (also commonly referred to as the GPz Turbo) against Yamaha’s XJ650LJ Seca. Kawasaki had delivered — albeit unofficially — the Z1-RTC in the latter part of the 1970s, but the ZX750 turbo was a true production unit and therefore better suited for this standoff. Both of the chosen combatants were based on existing offerings, but in keeping with their higher output mills were better dressed and equipped.


Getting to know them 

Following the debut of the original Z-1 in 1973, Kawasaki positioned itself as a dominant player in the high-performance market. Engines from the Z and later KZ models routinely found their way into championship-winning drag bikes and were widely considered to be among the strongest mills available. With other manufacturers exploring turbo power, adding a turbocharger was a logical step and created a new high-horse monster for Kawasaki.

Yamaha’s history was not carved from the same stone as Kawasaki’s, but the company had a number of diverse machines to its credit. Yamaha’s legendary 2-strokes and the XS650 twin and XS1100 inline-four earned high honors among riders on the street, and Kenny Roberts took the Yamaha banner to the winner’s circle repeatedly during the 1970s.

On paper, the ZX and XJ share a number of similar traits. Beneath their futuristic body panels they both have a tubular steel chassis carrying an inline-four engine. The similarities continue: The ZX wheelbase is 58.7 inches; the XJ measures 57.1 inches. Full of fuel and fluids the ZX weighs 556 pounds; the XJ 567 pounds. Seat heights are almost identical, falling within 0.3 inches of each other with 30.7 inches for the ZX and 31 inches for the XJ.

But even in their commonality, they are very different machines. The ZX mill displaces 738cc; the XJ 653cc. That difference in displacement gives the Kawasaki a 10hp edge over the Yamaha, with a claimed 95hp at 9,000rpm. This bump in power shows up at the drag strip, with the ZX trumping the XJ by more than a second in the quarter mile at just over 11 seconds against the XJ’s 12.68-second time.


A major contrast between the two bikes is their method of fuel delivery. The XJ uses a bank of four Mikuni 30mm carbs while the ZX features electronically-controlled fuel injection. This provides the ZX with enhanced go-juice delivery and seamless response when the throttle is yanked open.

A power-robbing feature of the XJ may be the final shaft drive, whereas the ZX uses a chain, allowing more of the engine’s power to reach the rear tire. This choice of hardware may also tell us a bit more about the intentions of the XJ as a sport-touring mount versus a balls-out performance ride. The ZX has a pair of discs up front and one at the back, where the XJ relies on dual-disc front and a drum rear.


On the road 

To get these great bikes out on the road, we called in two experienced riders for their seat of the pants input. In the yellow helmet is Sandy Callas. With more than 35 years of riding experience under his lid, he brings a wealth of knowledge to the table, and having owned a bevy of vintage and modern Japanese machines, he’s a good contrast to silver-helmeted Ken Rottmann, who takes the other side of the ring. Ken matches Sandy for riding time, but his interests lean toward the British end of the pool.

Getting familiar with the bikes, both riders found the Kawasaki to be a far more aggressive machine in every way, from seating position to throttle response. Sandy has owned numerous GPz models through the years, and he found the turbo Kawi similar to the bikes he’s owned, with the obvious difference of more power. Ken mentioned that the turn-signal cancelling on the Kawasaki is cumbersome and a bit distracting while in traffic. Maybe it’s the performance aspect of the ZX’s design that kept it from being as comfortable, too, but Ken felt cramped in the seat and thought a shorter rider might feel more at home. Sandy’s overall impression of the Kawi was about the same, labeling it a sharper-edged machine than the Yamaha. Ken also disliked the top-of-the-tank location for the Kawi’s gauges, saying they were hard to read, forcing the rider to take his eyes off the road. Both riders thought the Kawi’s windshield was too short, providing far less protection than the Yamaha.

Back in the day, the motorcycling press had lots of praise for the Kawasaki. "The Kawasaki T-bike is … the quickest and fastest turbo by a substantial margin. ... Granted, the other turbos are 650s and the Kawasaki is a 750; nevertheless, when you’re talking horsepower, the numbers win," said Cycle magazine in its November 1983 issue. "No normally-aspirated 750 — and few normally-aspirated anythings — can best the Kawasaki’s turbo-pressurized acceleration, its headlong rush, its willingness to leap from 60 to 120 mph in what seems like less time than it takes to read this line," said Cycle World in March of 1984.

The Yamaha, on the other hand, is a different beast. Ken thought the XJ felt heavier than it was, but also liked the XJ’s more comfortable riding posture. Sandy also called the XJ a "softer" machine, but again admired its comfort. Both liked the wind protection of the XJ, and both riders suggested it was likely the better sport-touring mount of the pair, capable of providing comfort and performance over long distances. Having once owned this exact Seca turbo, I can attest to the bike’s overall ease of use and comfort when ridden on long expanses of macadam.

Although the Seca was considered docile when out of the boost range, things get very interesting when you breach the 6,500rpm notch on the tach. The rush at that point is immediate and urgent, quickly pinning the ridiculous 85mph speedometer. The Kawi is similarly explosive when it comes on boost, and the press seemed surprised by the bike. Before the Kawi, the Honda CX500 Turbo was the only Turbo bike out there, and most testers found the Seca to be a much better overall package. "The Turbo Seca transforms itself from motorcycle to superbike and back again with ease, and the transformation is simply controlled by the right wrist. No phone booths, full moons or other props are needed," said Cycle World in its June 1982 issue.

Who wins? 

Terrific mirrors allowing riders to actually see behind themselves combined with easy-to-use turn-signal cancelling add up to more votes in favor of the Seca. Styling-wise, the Seca uses sharply creased panels and contrasting graphics for a far more space-age look that some think has aged poorly. The Kawasaki’s panels all flow as one, leading the eyes from the nose to the tail in a seamless fashion. The red and black motif accented by silver panels adds mystique to the overall appearance, and most think it’s a generally more handsome machine.

Looking them over, it seems that both of these variations on the turbo theme filled a different niche. The boosted power of the middleweight engines is a welcome feature on both, but the way they use and handle their newfound power is what sets them apart.

Ultimately, the insurance industry made it all but impossible for anyone to afford the required coverage on these puffer bikes, leading to their premature demise. The engineering, design and function was truly cutting edge for the day, and that has put them high on collectors’ lists as the market has finally embraced Japanese bikes as something worthy of attention. Not every model from Japan is loved or coveted, but the turbos are blowing in strong — just like they perform. MC 

Source Motorcycle.classic com