Kawasaki GPz 900R Ninja


Make Model

Kawasaki GPz 900 Ninja / ZX900R Ninja


1989 - 90


Four stroke, transverse four cylinder, DOHC, 4 valves per cylinder.


908 cc / 55.4 cu-in
Bore x Stroke 72.5 x 55 mm
Cooling System Liquid cooled
Compression Ratio 11.0:1


4x 34mm Keihin CVK34 carburettors


Battery ignition, full electronic! 
Starting Electric

Max Power

108 hp / 80.5 kW @ 9500 rpm

Max Torque

8.7 kgf-m / 62.9 lb-ft @  8500 rpm


6 Speed 
Final Drive Chain
Frame Iron, Double cradle frame

Front Suspension

41mm Telescopic forks, air assisted four way anti dive.

Rear Suspension

Uni-Trak air assisted, single shock, 4-way adjustable damping.

Front Brakes

2x 300mm discs 4 piston calipers

Rear Brakes

Single 250mm disc 2 piston caliper

Front Tyre


Rear Tyre

Trail 91 mm / 3.5 in
Wheelbase 1425 mm / 56.1 in
Seat Height 790 mm / 31.1 in

Dry Weight 

228 kg /  502 lbs

Fuel Capacity 

22 Litres / 5.8 US gal

Consumption Average

40.8 mpg

Standing ¼ Mile  

11.3 sec

Top Speed

247.8 km/h / 154 mph

For the GPZ900R from 1989 the change to 17" front wheel, the brake-size increases and the brake-caliber changes to be a 4-piston design,
the front fork diameter also rises to 41mm,

The GPZ900R was the machine with which Kawasaki recaptured its reputation for unbeatable four-cylinder performance. When the firm's first liquid-cooled four stormed onto the streets in 1984. the manner in which it delivered 150mph (241km/h) top speed with smoothness and unprecedented refinement confirmed that a thrilling new era had begun.

And there was much more than sheer speed to the bike that in most markets was known as the Ninja. This was a 908cc machine that felt as compact as a 750 - and which outran its 1100cc rivals when you opened the throttle. Street riders took to it in droves, production racers adopted it as their own.


Almost everyone who rode the Ninja was won over by a machine that combined speed with reliability, handling, comfort and its own unmistakable style.

Kawasaki had spent the previous decade earning a reputation for brilliant air-cooled eight-valve motors, but the GPZ unit was distinctly different. As well as liquid-cooling, it featured a 16-valve cylinder head plus developments including a balancer shaft, camchain at the end of the crankshaft, and alternator above the six-speed gearbox. It was small, light and powerful, though its peak output of 113bhp at 95()0rpm was slightly below that of the old GPz1100.


The rest of the GPZ maintained the theme of high performance with minimum size and weight. Kawasaki called the bike's frame layout a 'diamond' but essentially it was a steel spine design that used the engine as a stressed member, and which dispensed with the conventional downtubes. Aluminium was used for the square-section rear subframe. the box-section swingarm. and the large alloy footrest hangers on which it pivoted.

Front forks were 38mm units incorporating an anti-dive system that increased compression damping with suspension travel. Rear suspension was by Kawasaki's Uni-Trak monoshock layout, with an air-assisted shock unit that could be adjusted for rebound damping. The front wheel was 16 inches in diameter, following the fashion of the day.


Searing speed

The sharply styled full fairing did a reasonable job of shielding the rider, who leant forward to fairly flat handlebars. The Ninja was low. sleek - and most of all it was fast. Due to its superior aerodynamics it had a top-speed edge over its GPz1100 predecessor, with dramatic acceleration above 6000rpm and searing speed from 5000rpm to the 10.500rpm redline.

And the rest of the bike did not let it down. High-speed stability was exemplary, partly due to suspension that gave a superbly taut feel at the expense of some harshness at slower speeds. At over 5001b (227kg) the 900 was no lightweight, but by superbike standards it was very manageable, and its twin front disc brakes were hugely powerful. The Kawasaki was also practical, combining a generous fuel range with reasonable comfort plus neat details including luggage hooks and a strong pillion grab-rail.


The Ninja's success when launched was predictable, but even Kawasaki must have been pleasantly surprised by its long life. The 900 outlasted its intended replacements, the GPZ1000RX and the ZX-10. and even in 1990 was not replaced but merely updated. The front wheel grew from 16 to 17 inches in diameter; both wheels were widened to allow fitment of fatter tyres; forks were thickened to 41mm; and front brake discs were enlarged to 300mm and treated to new four-piston calipers.


As it remained in Kawasaki's range during the 1990s, the once mighty Ninja came to be regarded as a budget-priced sports-tourer rather than a serious high-performance machine. But that should not diminish its reputation. What should be remembered is that in 1984 the GPZ900R was the undisputed king of the road. And that it started the dynasty of liquid-cooled, 16-valve Kawasaki fours that continues to this day.

Source of review: Fast Bikes by Roland Brown