Kawasaki GPZ 600R Ninja


Make Model

Kawasaki GPz 600R Ninja / ZX 600R Ninja


1989 - 90


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


592 cc / 36.1 cu-in
Bore x Stroke 60 х 52.4 mm
Cooling System Liquid cooled
Compression Ratio 11.0:1
Lubrication Wet sump


4x 32mm Keihin CVK carburetors



Starting Electric

Max Power

75 hp / 54.7 kW @ 10500 rpm

Max Power Rear Tyre

69 hp @ 10500 rpm

Max Torque

5.1 kgf-m / 36.8 lb-ft @ 9000 rpm


6 Speed 
Final Drive Chain

Front Suspension

37mm Air assisted forks, AVDS adjustable anti-dive
Front Wheel Travel 140 mm / 5.5 in

Rear Suspension

Single air assisted shock adjustable for rebound damping
Rear Wheel Travel 130 mm / 5.1 in

Front Brakes

2x discs 1 piston calipers

Rear Brakes

Single disc 1 piston caliper

Front Tyre


Rear Tyre


Dry Weight

195 kg / 430 lbs
  217.0 kg / 478.4 lbs

Fuel Capacity 

18 Litres / 4.7 US gal

Consumption Average

47.8 mpg

Standing ¼ Mile  

12.7 sec / 107.3 mph

Top Speed

205 km/h / 127.5 mph

There is a problem with the GPZ600R. As Paul Taplin of Bike Sparks bemoaned, They're too good by far. Bikes like this are no good for business.' You wouldn't get a quote like that out of Kawasaki themselves, since the mid-size Ninja has been a good earner for them since it came out in 1985; so good in fact that, even when they finally produce a replacement model, they can't bring themselves to drop the Z from the range. Call them sentimental fools. Better, call them astute businessmen.

The simple fact is that Kawasaki are all but unbeatable at building in-line fours that go like hell and don't fall apart. In 1981 they started the excellent GPZ550 line and in 1984 brought out the GPZ900R, the big Ninja that left many people speechless with admiration. All of this was a rock solid basis for a middleweight to take over when the 550s got a bit rounded in the tooth. If this was Honda they would probably have junked all that knowledge and produced a two-stroke triple or something (the NS400R came out at about the same time) but Kawasaki simply ploughed all that knowledge back into the design and up came the GPZ600R.

Sorry if that sounds a bit like a press release, but to be honest the little Ninja was one of my all-time favourite bikes of the mid-80s. It was fast, furious and fun with bags of style and some surprising strong suits considering that it was based on a bike that had first come out five years before. The major difference between the 550 and 600 was the water-cooling. This allowed a more compact motor, with significantly smaller dimensions including less weight. Unlike the 900R, the camchain for the two cams came up the middle of the pots, with chain primary drive and alternator on one end. To save weight both alternator and timing covers were made of plastic.

Needless to say, there were four valves per cylinder and six gears, but no balance shaft since the engine was rubber-mounted at the front and forces within the engine were fairly well balanced. Carbs were 32mm versions of the aluminium semi-flat sliders found on the 900R while the steel four-into-two exhaust kept things fairly quiet without strangling the power. Power was claimed to be75hpat10,500rpm.

Around it they wrapped a steel rectangular-section frame with Uni-Trak box-section rear end, a proven set-up. The result is a neat and small bike weighing in at a really useful 430lb. With weight like this you can look forward to a crisp ride, without any of the compromises necessary when you have to take into account another 1001b, as you have to with a lot of bigger but not necessarily faster machines. The fairing was wrapped round this little lot, ABS top half, heat and abrasion resistant PBT plastic lower half, in a wind-cheating configuration so long as the rider was small and lay on the tank when popping out for some fags.

 The only silliness among all this stripped down leaness were the two bars which connected the fairing rear to the main frame rails. These were there purely for aesthetic reasons, drawing the eye down the line the designers had in mind. Designer nonsense but not as silly as some of the designer engineering that has been foisted on us since.

Even now, several hundred years later in bike terms, the 600 looks a beaut, being extremely compact - which is another way of saying that it is a bit of a pig to work on since everything is fitted in like a jigsaw. However, to hell with that, let's ride the thing. On the road it's a really great bike, being excellent in just about every department, which of course lays it open to a charge of lack of character, blandness, from some journalists who like to fight their bikes all the way to the ditch.

I went to Ireland on one for a week and had a wonderful time. The roads there are almost as bad as those in central London, being full of potholes, enormous bumps and craters, half-finished roadworks and homicidal or drunk motorists, all driving very slowly with brain speeds to match. The only difference to London is the addition of plenty of wildlife like donkeys, which even London hasn't resorted to yet, although continued transport strikes could see some entrepreneurial Greek making a killing every Wednesday if the thought occurs to him.

We digress. Only a pukka motocross bike

could cope with the roads over there, so although the GPZ did its best the editorial bottom was either being clouted by the saddle or was soaring skyward. GPZs land well after bumps. What was really impressive was the nimbleness of it, the way it would whip down lanes, pirouetting round obstacles mobile or stationary, brake, change gear, direction and pace and be off again. Mid-range go is not wonderful but is adequate so long as you're not about to be crushed between a donk and a drunk driver. In such situations a quick flap with the left foot a couple of times will get you out of the trouble you got yourself into.

Back on the relatively wonderful roads of countryside Britain, the GPZ really came into its own. The 37mm forks and firm chassis give a supremely taut ride, while the triple discs work faultlessly with plenty of information fed back to the pilot. The free-rewing, free-breathing engine really is a jewel. You can trundle around quite happily at lowish revs, all day if you are feeling relaxed but, like a TDR or a YPVS, it's hard not to let the revs rise toward the 11 .OOOrprn redline. If you keep the revs up you can make really rapid progress and have an absolute hoot of a time. The engine is so well balanced and smooth that you don't even get the impression that you are thrashing the nuts off it, as one does on a two-stroke.

It always feels as if it has a balance shaft, but rubber-mounting at the front takes care of any vibration that comes out, so you are left with an engine that at most revs has no vibes at all, none whatsoever. You want  more? How about comfort good enough for

at least 150 miles since you sort of wedge yourself in and get on with it, although taller riders can find it a bit cramped. And here is the clincher: fuel consumption that can easily be in the high 50s to the gallon. On a fast motorway bash I got 200 miles between stops without any discomfort and returned 56mpg.

However, all good things must come to an end, and in this case it's the end for all the good things. Now the bad things. The clutch feels horrible, jerky and feeble, and the six-speed box gets clunky and notchy when hot. And the bike runs hot a lot of the time, with the fan cutting in often after only a few miles on average (cold) British days. If you were built along, shall we say, generous and accommodating lines, then you might have a problem with the dinky dimensions, but then you shouldn't gorge on so much disgusting fatty food and sugary beer but should exercise more, since heart disease kills thousands a year more than biking accidents.

The bad news pretty much ends there. On the electrical side they get a clean bill of health, and Kawasaki have had very few problems reported to them - although the GPX version and the '89 GPZ both get the carb heaters. Early models had problems with steering head bearings wearing fast but that was easily remedied by new seals stopping water getting in; a few others had brake judder problems caused by distorted discs and later models have the clutch cable re-routed to try and take some of the kinks out of it - partly successful, but it is still not one of the bike's better points.

The excellent Tony Galea of Galea Camchains (01 -885 5861) - who is now so famous that even the police recognise him when they stop him for alleged speeding -owned a GPZ600R for a while and grew to like it a lot, while discovering a rather idiosyncratic problem which has come up with other bikes he has seen. The symptoms are that the bike won't idle, tends to cut out on two, and generally behaves in mystifying manner with a hint at the carburation. In fact it is the pulsers (described by him as 'the twiddly bit on the end of the crank') which are heading East. Change them and normality returns.

At the time of its inception, there was something of a camchain debate going on in Japan, with two schools of thought. One was that a light camchain would not be substantial enough to cope with the power it would have to transmit, while the other side felt that a heavy camchain flying around would actually contribute to any problems. Kawasaki, in a land of indefatigable gamblers, seem to have covered themselves here since the 900 Ninja had a whacking great camchain and the 600 has a petite, seven-plate morse chain. Result? The 900 runs, albeit belatedly, into a load of camchain problems and the 600 runs on for at least 30,000 miles with no problems at all. If you have a high-miler with a problem Galea Camchains will put in a new, slightly heavier chain, re-do the tappets and so on for £90, which includes parts, labour and VAT.

Although the bike runs hot, it doesn't seem to cause too many problems or to affect longevity although Tony Galea recommends changing to 9-grade from the 8-grade plugs. A dodge is to change the early model's paper air filter for the later washable filter since it is interchangeable not just with early 600s but with the 550s as well. Since they are about the same price this could represent a useful saving - part number 110131157. Other points to watch are obviously the Uni-Trak linkages, so get the bike up on the centre stand and check for lateral play. With a secondhand bike there is bound to be some, but too much can prove expensive to rectify. If the exhaust is shot, a Motad Datum system comes well recommended, improving the mid-range, where the original bike is weakest.

The final point to watch is that the bikes don't like a lot of slow or town riding. Despatch riders have had problems with just riding round London all day. The 16 valves are really rather tiddly and are prone to carboning up, eventually holding the valves off their seats. A decoke or regular fast rides in the country seem to solve that, which sounds like a pretty pleasant way to keep your bike fit.

When the GPZ600R A1 came out in June 1985 it cost a fairly reasonable £2949, which has now risen to £3749, which is pretty fair for four years of rising costs and escalating Yen values. The only real differences in that time are for this year, when the GPZ, now ■ selling alongside the GPX600, got the latter's cylinder head, pistons and conrods. The GPX, at £3899, has seven more horsepower at 82hp and a bit more torque, but basically there has obviously not been a lot that the Kawasaki engineers have managed to come up with to improve an already fine design.

In 1986 the GPZ600 was the best selling middleweight in Britain, and only really lost that slot when Honda paid them the sincerest form of flattery and dropped their V4 middleweights to produce an across the frame four, the CBR600, which now holds top slot for middleweight sales. But the GPZ600R is more than just a major influence on this year's top seller, it is still a fine bike in its own right, still selling well and heading remorselessly toward sainthood. A scan through the weekly comic shows that a 1985 GPZ, which would have cost around £3000, is still worth at least £2000, perhaps £2500, four years later. A Kawasaki classic.