Kawasaki GPZ900R (1984-1991): Review & Buying Guide

Kawasaki’s GPZ900R is arguably the finest bike of the 1980s. Not only a huge hit with road riders and proddie racers alike from its showroom debut in early 1984, this inline-four superbike outlived its successor, the GPZ1000RX, by four years in the UK and 16 years worldwide. It then outlived its successor’s successor, the ZX-10, by a year in the UK and 13 years in Japan – for a litre-class superbike that’s simply unheard of, but it explains the 900R’s enduring appeal as a sought after modern classic.

Before the GPZ, all Japanese superbikes followed the same flawed recipe: plonk a big, powerful motor in a basic chassis and hope for the best. By the late 1970s power outputs far outstripped the capability of frames, suspension, brakes and tyres. Kawasaki addressed this with the 900 by building a chassis that could compliment a new, lighter, more powerful engine, and in doing so created the blueprint for the modern motorcycle. In fact Kawasaki got it so right with the GPZ900R that this now 40-year-old classic still feels competent, rewarding and rapid, with ergonomics that not only maximise control and feedback but also work as well over distance as they do on a short blast.

But the GPZ900R is much, much more than the result of remarkably on-the-ball design. It’s a cultural icon too – who can forget Tom Cruise blasting his 900R off into the sunset on Top Gun? Despite rumours that Tom’s Ninja was a 750, it was a 900, bought by the production company and painted in non-logoed 750 colours at Cruise’s request after Kawasaki refused to supply a bike FOC. The Japanese brand certainly got the last laugh because the GPZ will forever be linked to one of the most successful movies of all time.

Remarkably, for such a successful and legendary machine the 900R remains not only popular but affordable too, which is great news for anyone looking for a truly rewarding modern classic. Tidy examples start at around £2000 with minters rarely making more than £5500, so the GPZ is still a whole lot of bike for the money. And here’s how to bag yourself a belter…

Pros & Cons

1984 Kawasaki GPz900R - Prices

1984 GPZ900R A1
New model, known as a ‘Ninja’ in the States. All-new liquid-cooled, DOHC, 16v motor with left-side camchain. Distinctive Darth Vadar styling. Claimed 115bhp and 228kg dry weight. Potential for 154mph. Colours: red/graphite 

1985 GPZ900R A2
Fresh graphics and colour options. Revised top shock mount bolt. Colours: red/black, blue/silver, green/white, silver/red 

1986 GPZ900R A3
Carb icing solved by a heating circuit, running warm water from the cooling system around the carbs. Cam pitting issues with early models addressed by fitting wider diameter oil pipes. Model logo moved from side panels to fairing and changed from GPz to GPZ. Colours: red/black, blue/silver 

1987 GPZ900R A4
Colour changes only. Colours: red/silver, blue/silver 

1988 GPZ900R A5
Colour changes only. Colours: red/silver, black/grey 

1989 GPZ900R A6
Colour changes only. Colours: black/graphite, black/silver/red 

1990 GPZ900R A7
First major changes – new 17in front wheel, and both wheels now 3-spoke in design. New tyre sizes (120/70 17, 150/70 18), new fork, now minus ADVS anti-dive. Colours: red/black, black/silver/graphite 

1991 GPZ900R A8
Colour changes only. Model discontinued in the UK after 1991. Colours: red/black, black/silver/graphite

 *A9 model sold in Japan from 1992 through to 2003.

Kawasaki GPZ900R values:
Rough £900-£1600
Tidy £2000-£3500
Mint £4500-£5500

1984 Kawasaki GPz900R - Engine & Performance

Kawasaki has always understood the importance of heritage and brand loyalty, so the GPZ’s 900cc capacity was no accident; rather a significant nod to the legendary Z1. The bike’s inline-four motor was all new, however. The most significant change from the firm’s older Z and GPz engines was the change to liquid-cooling – a move critical for both reliability and outright performance.

Minimising size and weight was another key component of the 900’s overall design. Moving the cam chain from the centre of the engine, as per air-cooled Zeds, to the motor’s left side helped shrink the unit’s width by 127mm compared to the original Z1. Combustion efficiency was maximised by topping the unit with a compact DOHC 16v cylinder head – valve angle was pinched to a narrow 34.9° to save space, while 34mm semi-flat slide Keihin carbs flow mixture into the top end. A compression ratio of 11:1 was higher, Kawasaki claimed, than any other big bike of the time. The result was an engine 5 kilos lighter than the Z1 able to rev to a heady (for the time) 10,500rpm.

Performance from the engine was impressive. Kawasaki claimed 115bhp at 9500rpm and 63lb.ft at 8500rpm, giving the 900R a top speed of around 155mph depending on conditions. One brochure of the time even claims 157mph – either way, the GPZ’s potential and performance was mightily impressive, with plenty of lowdown drive, rich midrange stomp and a searing top end drive that proved a match for all opposition of the time. A Proddie TT win at the hands of Geoff Johnson did the GPZ no harm either.

Even 40 years on a fit 900R still impresses. It’s still a seriously rapid road bike, despite its power output being only modest by modern standards. The biggest hint that this motor is four decades old is initial pick up from a closed throttle. There’s a big heavy crank underpinning the engine’s design and it takes a moment or two for it to spin up. But once on cam, this motor still delights and engages in equal measure.

1984 Kawasaki GPz900R - Handling & Suspension (inc. Weight)

By 1984 racing inspired perimeter frames were taking over from the previously favoured cradle design, but Kawasaki took a different route with the 900R adopting a lightweight tubular steel spine design (they called it a Diamond frame) which gained rigidity by using the engine as a stressed member. Not only did this solution save a significant amount of weight, it also increased ground clearance.

Up front the GPZ was given a set of 38mm Kayaba forks featuring Kawasaki hydraulic AVDS (Automatic Variable Damping System) anti-dive tech – very much the cutting edge of front suspension design at the time. At the rear a box-section aluminium swingarm with eccentric adjusters and rising-rate Uni-Trak suspension, again controlled by a Kayaba damper. Wheels on A1 to A6 models are 16in front and 18in rear; from the A7 a 17in front took over alongside conventional forks minus the by then outdated anti-dive system.

What impressed most about the 900R’s chassis – and still does 40 years on – is its balance of accurate, responsive handling and unshakeable stability, a combination rarely delivered by big bikes of the time outside the likes Bimota. In 1984 the 900 cornered and rode more like a lithe middleweight than a large capacity superbike – it was a revelation. Even today a well maintained 900R will ride with a poise and intent that belies the design’s years.

Braking is average by modern standards – single-pot calipers can only deliver so much. But with braided lines in place the system is enough to haul this big Kwak to a halt without too much drama. The later A7’s twin-pot front units offer far more punch and feel.

1984 Kawasaki GPz900R - What to look for

Cam Train
Early models (A1 and A2) suffered from cam pitting issues due to insufficient oil reaching the top end. The problem was cured on the A3 by the fitment of wider diameter oil pipes. A1-A2 bikes were not recalled for this issue, so ask the owner if new pipes have been fitted. Cam chain rattle is fairly common too. Replace the chain at 50,000 miles and go for a manual tensioner. 

Sprag Clutch
Like so many large capacity engines, the GPZ’s motor needs a full, healthy battery to turn over its heavy crank. Attempting to start a 900R on a low or weak battery can ruin the starter clutch. Can be an issue on high mileage engines too. Replacement requires an engine strip. 

Engine Temp
The French referred to the 900R as ‘Le Percolator’ on account of the model’s propensity to run extremely hot and/or overheat, particularly at low speed on a warm day. Get a test ride and check that the fan kicks in when the engine temp rises. Many owners fit a manual fan switch. 

Suspension Linkages
Have a good look underneath. Also pop the bike on its centrestand to check for freeplay in the suspension linkages. Said linkages should be greased at least every two years – needle roller bearings at the front of the linkage are often left ungreased on account of their inaccessible location. This is folly because they’ll fail. Whip the whole unit out at service times and be generous with the grease. 

Sidestand
The sidestand cut out switch is also the earth for the CDI unit, so misfires and poor/non running can be traced back to this component. Taking it out, giving it a clean and lube is good practice. 

Fuel Tank
A haven for rot, particularly on the lower left side seam if the bike’s been left for extended periods on its side stand – moisture runs down the tank and gathers on the seam, leading to rot. Check for paint bubbling, rust and any hint of pin holes. If a bike had been stood on its side stand for a while, moisture can also gather in the left side plug hole in the head. This can cause a misfire. 

Exhaust System
Very few original systems will have made it through the last 40 years without rotting out and being replaced by an aftermarket pipe. Marving make a twin silencer system that’s as near in look to the original as you’ll find. Downpipes rot, often from the inside out due to condensation. 4-1 systems can rob the engine of midrange grunt and often need to carbs jetting to suit. 

Brakes
Disc warpage can be an issue. Poorly maintained calipers lead to corrosion behind the dust seals which in turn prevents the pistons from returning properly causing the pads to drag on the discs. This creates heat and the discs to go out of true. 

Carb Icing
An issue with many a Kwak of the era. The issue was cured by Kawasaki (from the A3 model onwards) fitting a carb warming kit, running a circuit of hot water from the cooling system around the carbs. Carb icing can be potentially dangerous; the carb slides can stick, causing the throttle to stay open.

1984 Kawasaki GPz900R - Rivals

1984 Honda VF1000F - Honda’s first litre-sized V4. Sophisticated for the time and a decent motorcycle, but damaged by association due to top end troubles of the VF750S and F. Early VF-Fs are half-faired with a bellypan, and look a treat. The update – the FII features bigger wheels and the Bol d’Or model is fully faired. Not as neat, precise or engaging as the GPZ, so sales were steady rather than impressive. The sportier styled VF1000R is a different animal, but still feels like a tank compared to the 900R. 

1984 Suzuki GSX1100EFE - Bigger and heavier than both the 900R and FJ1100, so can be a bit of handful on B roads and twisty A roads. Was sold as a naked (E model), half-faired (EF), and fully faired (EFE) guises. Quite rare now in faired spec – both 900R and FJ were way more popular at the time. Immense engine – utterly bulletproof and still used by drag racers on account of its robust design and tunability. Can command strong money on account of the engine’s desirability for project bikes. 

1984 Yamaha FJ1100 - Launched as a sports bike and was a direct competitor to the original 900R, then mellowed into a super-fast sports tourer in 1200 form. Immensely strong and grunty engine, very comfortable over distance and remarkably manageable through the twisties. Later (1986-on) FJ1200s are better as a package – more oomph, better protection from the elements, and detailing. Like the 1990-on GPZ the FJ also, from ’88, received better brakes and wider rubber. And like the Kawasaki this Yamaha remains desirably affordable.

Honda VF1000FII, 1984 | Approx. Price: £1500-£3000

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Power/Torque

122bhp / 66lb-ft

Weight

238kg

Suzuki GSX1100EFE, 1984 | Approx. Price: £3000-£5000

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Power/Torque

114bhp / 72.3lb-ft

Weight

238kg

Yamaha FJ1100, 1984 | Approx. Price: £1500-£3000

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Power/Torque

125bhp / 64.2lb-ft

Weight

227kg

1984 Kawasaki GPz900R - Verdict

The GPZ900R is a special motorcycle. So good it outlived two replacements and is still astonishingly competent – and quick, even 40 years on from conception. Condition is the key when buying, so it’s worth spending a bit more to secure a minter. A cheaper runner could quickly turn into a money pit when exhausts, suspension, brakes and electrics require an overhaul. But if you want a genuinely legendary ’80s sports bike that still delivers today, you won’t go far wrong with a neat and tidy 900R.

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1984 Kawasaki GPz900R - Technical Specification