Unlike the other Japanese companies, Kawasaki pursued the perfection of the aircooled, two valve, DOHC four cylinder engine long after they switched over to their watercooled designs in the mid eighties. In particular, the GPz550 mill was almost unaffected by its lack of technology, becoming faster and more economical with each succeeding model. Larger models in the range were more limited by their relatively simple designs but nevertheless can still be put on the pace with some minor mod's.
Their basic usefulness means that there are still plenty on the used market. Ranging from rats with barely running engines to low mileage, well cared for, bikes. Between those two extremes, there are an awful lot of clean, neat and mildly modded machines. The basic engine design lives on in both the GT550/750 and the Zephyrs - however, neither of these ranges offer the mix of speed and practicality of the GPz's, as ever more strident noise and emission laws have left the engine design much muted, though no less tough. Either GT's or Zephyrs can usefully be modded into more exciting playthings - and their prices are moderate.
Good GPz's fetch serious money, up to two grand even for the smallest of the bunch. The reason for this is that they were the kind of bikes that attracted the boy-racers, who just loved to thrash them to death. The ones that weren't ridden with a death-wish thus command high prices because they remain very useful pieces of tackle. However, the engines were basically tough old things that responded to a modicum of attention with excellent longevity, so even the ones with tatty chassis are worth a look, if not a large wedge.
The GPz550 was the best of the bunch in terms of merging speed and frugality, as well as being the nicest handling on the back of its relative lack of mass and power. The kind of bike that could take the daily commute through Central London with something approaching elan - if not narrow it was at least easy turning and moderately comfortable at town speeds. Used mildly but by no means slowly, it had the ability to turn in 60 to 70mpg and not destroy its consumables in short order.
On the other hand, it was equally at home cruising the motorway at ton plus speeds and shooting down country lanes at improbable velocities and angles of lean. Fuel would still hover around 55mpg unless really thrashed when it went down to 45mpg. Although its screen was too low, the fairing managed to take a large amount of the wind and rain off the rider (and, indeed, inspired a few aftermarket versions which had even better protection).
A machine for all seasons, that in the overall analysis is hard to fault. This is more true of later models than earlier ones. An almost unique example of continuous improvement rare in the seventies and eighties (though not the high tech nineties).
Not least in the design of its camchain tensioner, the weakest component in the engine. This was inherited from the Z550, which in turn was inspired (if that's the right word) by the Z500, though the engine can trace its roots back to the Z400 (even though it shares neither bore nor stroke). The earlier the bike the more likely it is to fail, not just down to old age and high mileage, also because minor improvements were applied over the life of the model. Whereas an '89 550's tensioner might last 40-50,000 miles, an '83 model might manage only 25000 miles.
Worse still, various bodges can be applied to the tensioner to get the bike out of the street or showroom. A naff tensioner or camchain isn't the end of the world, can be fixed for around a 100 sovs without splitting the crankcases. Don't ride round with a rattling camchain, if it breaks the valves and pistons end up mashed.
The valvegear's the toughest in the business, needs little maintenance, though it is possible to burn the valves or the guides out from chronic lack of maintenance or mismatched exhaust and carb jetting. As the standard exhaust system's quick rot, 4-1's are all too common. As the engine's highly tuned they can turn the power delivery a bit finicky but well matched jetting does give a bit more power and a lovely howl above 7000 revs. Easy enough to check out on the test ride.
Some engines need a rebore around 50,000 miles, but 75000 miles is possible on motors that have received regular doses of clean oil and filters. Good engines have a nice mechanical rustle, entirely lacking any rattles, taps or knocks. It's always worth taking the engine breather pipe off the airfilter to check for fumes (usually a sign of valves or piston rings going down).
The bottom end's good for at least 75000 miles, maybe over a 100,000 miles on more moderately used machines. The most we've seen on a GPz550 clock's 145,000 miles, the owner claiming that it was more or less stock - if you've done more let us know. Most bikes have now done at least 30,000 miles, not the end of the world but some care needed when looking them over.
Curiously, time and time again, we've seen examples in dealers with 15-20,000 miles on the clock that look and sound like they have done over 50,000 miles. One salesman turned rather nasty when this was pointed out, all but foaming at the mouth about us wasting his valuable time. What seems to happen is that some hard ridden GPz550's traded in for one of the 600's replicas and the dealer then clocks the machine to make up for the large trade-in value he's allowed. Worth watching out for!
We've seen those kind of bikes priced in dealers at £2000 to £2500, though no doubt they will come down quite a bit if lots of dosh is waved under their noses. However, on the private market two grand buys a really immaculate example, which is bargain time because they really are the best of the old style 550's, and something with less than twenty thou on the clock has loads of life left.
At the other end of the market, the ratty but running examples come in at £500 to £600. These are a mixed bag in which neglect has eaten deeply into the chassis and the state of the engine's basically down to how often the oil's been changed. Troubled engines show their anger at neglect in an excess of rattles and smoke, plus a strict toning down of the normal seven grand power punch.
If you're lucky, you'll find a rat with the carbs way out of balance but the rest of the engine basically okay. Carbs out of balance cause the clutch to rattle with a death-wish, the engine churns out secondary vibes (even on the later rubber mounted engines) and performance becomes pathetic. The carbs may be out of balance because they are worn out (after 60,000 miles), which makes fixing them somewhat more expensive. However, all the problems caused by worn or out of balance carbs are also caused by a knackered engine!
Engine spares are difficult but not impossible in breakers. Whole engines, from the same source, are usually well knackered, as crashed bikes are usually repairable (and difficult to suss other than in the sometimes loose handling). Chassis spares are similarly difficult going but many minor items are common to the other Kawasaki models and it's not impossible to fit front ends off other bikes.
Not a bad idea, as by now many of the twin discs will be in a sad condition. They were state of the art in the early 80's, which doesn't say much and basically means they need some muscle, aren't totally homicidal in the wet and can squeal the tyres from moderate velocities. After a time, crap gets into the calipers, the discs score and warp, and the master cylinder often cracks in minor accidents. They are often too far gone to repair, but fairly easy to suss.
The only other chronic weak spot in the chassis is the Uni-trak's bearings which when newish need a yearly grease session but by now will require a six monthly going over with the grease gun. When newish, handling's close to excellent, when the wear gets into them the bike weaves and wobbles, sometimes very viciously. It's easy to blow over a hundred notes sorting it out, sometimes it's so seized and worn that the only way to get it apart is by destroying it!
Unlike GS Suzuki's, the charging system's generally tough. However, the electronic ignition modules are susceptible to demise at high miles, usually when their rubber mounts go hard and let the vibration through. Although, worn engines churn out enough vibes to take them out even if the rubber mounts are okay. Extra rubber mounting's the order of the day, as they are rare in breakers and expensive from dealers. At least it's easy enough to check, as duff ignition stops the engine working!
The earlier GP550 was rather more troublesome than the GPz550, sharing most of its engine with the Z550 whilst inflicting a lot more power on its components; such troubles compounded by it being the type of bike, back in '81 when there were few rivals in this category, that attracted the crazier owners.
The camchain tensioner can last for less than 20,000 miles, valvegear wear can be quite advanced at this mileage and even the bottom end can start rumbling at as little as 50,000 miles. The engine's also quite hard charging, not so useful at mild riding at lower speeds as the GPz - time tends to ruin the power delivery via rotted exhausts or airfilters full of crap or worn carbs.
By now most chassis will have been upgraded with better forks, shocks and brakes - if they haven't any speeding will soon have them off the road. There are some that have been neatly renovated, a few rats and even the odd stocker running around in a mild state of decay. The tatty ones can be picked up for as little as 500 sovs, but a grand should buy something with a little blood and guts left. But a decent but not immaculate GPz550 can be bought for around £1500, the extra money worth it in terms of value for money.
Most of the GPz550's problems apply to the larger models. The later 1100's had the dubious benefit of fuel injection. Sometimes this ran fine, other times it caused such hassle that some owners reverted to carbs. Just to confuse matters, if one of the injectors goes down the system's still quite capable of running the engine up to 6000rpm - when test riding make sure it runs cleanly to the red line. Also, any misfiring's a sign of the injectors going down. Both the injectors and their electronic modules are expensive to replace, good ones in breakers difficult to find.
With so many expensive bits of technology to go wrong, there's a huge downside to purchasing one of these bikes that has to be taken into account, although they are usually okay for the first 20,000, or so, miles.
The bike has bags of power, one hell of a kick over 6000 revs. 4-1's give it a nasty snarl at higher revs and the injectors can take mild changes in exhaust flow without complaint; if the exhaust's too radical it's pretty obvious in a stuttering power delivery (which might also be the injectors going down, just to confuse things).
The combination of excessive power and mass stresses the chassis. It's nowhere near as dangerous as a Z900, for instance, and can be ridden with muscle and bravery as fast through the bends as modern replica's, but it's wholly lacking in these bikes' civility and sophistication. Also, if any element in the chassis - tyres, bearings, suspension, etc - isn't up to par then in comes the weaves and wobbles. The aforementioned Uni-trak linkage wear is very obvious if you try to ride one of these bikes fast!
In the Kawa's favour, the engine's bottom end is based on the ultra tough Z900/1100, the only possible weak spot in the first 100,000 miles being the clutch which burns out when abused by the more crazed wheelie merchants. Valvegear and camchain wear can hit the engine at as little as 30,000 miles but it's really more down to the degree to which the engine's thrashed and neglected than any chronic faults.
Given the handling limitations and excess of power, many engines have a relatively easy life, last for over 100,000 miles without major attention. As with most Jap engines of this era, regular oil and filter changes are worthwhile. Secondary vibes at high revs are normal, can limit the bike's uses as a long distance tourer, as can the way it eats expensive tyres.
Really immaculate GPz1100's go for around £3000 in private deals. £2000 will buy something in good general order, with loads of life left, and blistering performance even by today's wacky standards. A grand will buy a bike with a nasty chassis, rattly engine and some wild times!
Early twin shock 1100's retained some of the handling excesses of the Z900/1000, though could usefully be upgraded with alloy swinging arm, decent shocks and later front end - even then it wasn't perfection on wheels, but the madness, the way the chassis would viciously bite back, was subdued, didn't appear until ton plus speeds came up. A fully modded twin shocker, with a stock engine (thankfully running on carbs), isn't a bad buy at £2000 to £2500, though it's not worth paying any more because you end up in the same price range as later replicas.
Whilst the 550 was versatile and fun, the 1100 blistering in performance, the GPz750 combined the worst of both worlds. Tanked up, it weighed close to 500lbs and didn't really have geometry that hid that mass (as some monstrous modern bikes manage to do), making it a bit piggish in handling in the same way as the 1100.
The 750's engine isn't the toughest of the bunch, either, with clutch, cylinder head gasket and valve hassles once over 50,000 miles. Some of them did last reasonably, up to 75000 miles without great expense - but the exception rather than the rule. A lot of its extra power is used up in hauling all its mass along, but the half fairing version's quite a useful ton-plus speedster.
The early twin shocker's one of the nastier handlers around unless the usual upgrade's done but it does have evocative styling if you're into early eighties bikes. The latter goes for around £1500; £2000 buying a jolly nice example of the later bike. The £500 rats don't really bear thinking about but you may get lucky.
The most interesting version of the 750's the one they cobbled on a turbocharger, marvellous power buzz when the turbo goes into boost mode. Nasty handling, finicky injectors and turbo components, plus sometimes the turbo destroyed itself due to overheating from a lack of lubrication. On the other hand, the Turbo's reputation is so low that it can be picked up for silly money in reasonable nick - a thousand notes for something with a hundred horses can't be sneezed at.
Overall, the GPz range is one of the more interesting and generally still up to spec even on our frenetic roads. The 550's the best bet, with most of the 750's performance and little of its hassle. The 1100's still a wild old thing that can tear arms out of sockets but can turn out a very expensive proposition. It's a pity Kawasaki don't re-invent them instead of the GT's and Zephyrs.
Dick Lewis