It’s such a good bike, some don’t class it as a classic. The GPz750 offers classic bike charm with reliable, modern manners for a very reasonable price.
Words by Oli Hulme
If you went to pubs that were hang-outs for motorcyclists rather than ‘biker pubs’ in the late 1970s and early 1980s, they were a good place to see where trends were going. Back then we didn’t call them trends; it was just about having the latest hot bike, not the big stuff, the Z900s or bevel Ducatis or Honda 750s, but the stuff younger riders could actually afford – with the biggest issue often being the cost of insurance. British iron gave way to Honda 400 fours and Z650s, and they gave way to Yamaha LCs, with and without L-plates, and then almost overnight, in 1982, all that white bodywork suddenly vanished and the rows of bikes turned red.
Kawasaki had launched the GPz 550 four. A reduced-capacity version of the Z650 engine had already arrived in the sensible-looking Z400 and z500 four, but this red rocket was something quite different.
Developing the GPz range
In the late 1970s, Japanese manufacturers didn’t just release a new bike and refine it before looking at replacing it – they started planning a replacement before a new model was released.
The smaller Kawasaki 500 four had become a popular racer in the USA, and Kawasaki paid attention, creating the GPz with an oversquare, two-valve, 553cc engine. It had higher compression and hotter cams, electronic ignition and an oil cooler. The UK version of the Z500 already had twin front discs and a single rear, and the GPz 550 gained unlinked air forks, better shocks, lower handlebars, and footpegs offering a racier riding position. A small fairing was fitted to the headlight, big enough to hold the clocks but which made little difference to the aerodynamics.
The paint job was what it was all about. Instead of the ‘mini Z1000 Mk II’ look of the z500, with paint in shades of dark metallic green, the GPz got all-new firecracker red. In a move that set the tone for styling to this day, most of the engine and all the exhaust system were completely blacked out, which was quite radical for the time.
It handled better than the Z500, but it still had a relatively unsophisticated chassis. Some riders felt this provided proper ‘feel.’ It could top 115mph and do 12.5-second standing quarters.
It was a massive sales success. Not being a company to rest on its laurels, Kawasaki added the slightly terrifying GPz1100 muscle bike in similar trim with an over-bored, fuel-injected Z1000 engine that was too powerful for its twin-shock chassis.
A year later, the GPz750 arrived with a bored-out and seriously updated version of the engine previously used on the more staid Z750 four and developed from the Z650.
While rival manufacturers Honda and Suzuki were heading into uncharted territory – Suzuki with its four-valve GSx motors, Honda developing its VF750 four-valve V4, and Yamaha ploughing its own slightly strange furrow – Kawasaki stuck with what it knew, just making its DOHC four better. To the casual observer, the motor was from the older models, but in reality it was all-new, with revised external. Two valves per cylinder were deemed enough, the valves operated by twin camshafts with buckets and shims – the shims mounted on top of the valve stem and under the bucket, rather than above the bucket as on the Z1000, which had seen some get dislodged with serious consequences. There were rubber mounts at the front of the engine to reduce the vibes getting to the rider. As on the Z650, the primary drive was by chain, rather than the gear-driven Z1000, which meant the GPz750 required an extra chain to drive the clutch. A bank of four 34mm Mikuni CV carbs provided the fuel to make the GPz750 go. Simple but effective, this engine stayed in Kawasaki’s line-up for another 22 years, finally powering the budget-priced ZR-7 750 which went out of production in 2004.
Alongside the twin shock 750, the 550 got a new look just two years after launch, the major change being the addition of the Uni-Trak suspension system which made it handle slightly better, while the bike itself retained a square-edged look.
Just a year after that, all the bikes got another set of new clothes, breaking away from their late 1970s and early 1980s styling. The second (or third, if you count the 550) iteration of the GPz was a significant departure for Kawasaki.
Rival Suzuki had been selling its striking Katana models since 1981, but the Hans Muth styling had split opinion and hit sales. The new GPz was given a similar but less extreme departure from the norm. There was an effective sharp-edged and swoopy upper fairing, and inside that there were many new and exciting things to look at. The speedometer was large and the rev counter small and they were mounted at a 30-degree angle to each other. The rev counter also doubled as a voltmeter – as long as you still had the special three-terminal Kawasaki battery – by pushing a button. There was a Christmas illumination of idiot lights on each side of the ignition switch with all the usual additions and an extra few, including one for each indicator and a hazard flasher function.
Below the yokes was a digital display which included a fuel gauge, an alert about your sidestand being down, oil pressure alerts, and warnings if the battery/charging circuit had a problem.
This was all radical stuff for 1984. The tank swept back and then the side panels and seat swept up.
The footrests were more rearset, and there was the interesting Kawasaki Uni-Trak suspension set-up with a single, air-damped shock. This wasn’t the same as the suspension fitted to the Mk2 550, which had the adjuster collar on the shock sitting under the swingarm. This was found to be hard to get at and it was also exposed to road muck. To adjust the suspension on the 750, the right-hand side panel was removed and with care the air in the shock could be adjusted through a Schrader valve. This new suspension arrangement on the GPz750 suspension system was designed to be compatible with US production racing rules. These required machines to use stock equipment, and the new version of Uni-Trak was derived from that fitted to the Kawasaki KR500 GP racer.
Weight lessening additions in the drive line included holes drilled in the inner links of the chain. At the front was an anti-dive system. This gave you bragging rights, but didn’t do anything really important for day-to-day riding, and when it failed, as it inevitably would, owners simply blanked it off.
By not overdoing the engine tech, Kawasaki cunningly left plenty of room for the owner to add performance mods of their own. While a stock GPz750 was slower than Suzuki or Honda alternatives, some attention to the valves and the exhaust and few extra teeth on the rear sprocket added several mph to the top speed. And the Kawasaki was, by comparison, easy to work on too.
By 1985, the GPz was up against more powerful rivals, including Kawasaki’s own GPz900R, Yamaha FZ750 and Suzuki 750 Katana with the pop-up headlight, the GSX750ES and the later GSX750-R, most of which handled better and had fancier engines, while Honda’s 750 vee-fours were increasingly much more mechanically sophisticated. And, after a brief attempt to clear remaining stocks by shoving a full fairing on it from the GPz750 Turbo, the 750 slot in Kawasaki’s line-up was filled by the slightly pointless GPz750R, a version the GPz900R.
Buying and running a GPz
Today, a GPz750 in moderate to good condition makes enormous sense. It is as tough as they come. You can still get decent tyres, the brakes are good enough for modern traffic, the lights are good, and the indicators are huge. Most parts are available, though carbs can be an issue, as with pretty much every Japanese bike from the 1980s. It didn’t change much in the three years it was sold in the late swoopy bodywork, and a lot of the bits are interchangeable with other models with a bit of fiddling. The exhausts will probably have rotted out by now, but 4-1 replacements can be found. The engines are pretty much bulletproof. The trouble with that is because the engine doesn’t break, the rest of the bike can get neglected.
There can be a bit of a clutch rattle, and the carbs can be troublesome. Diaphragms have been hard to find in recent years, but specialist NRP is currently offering to attach new ones to carbs slides. Many were fitted with cheap pod filters, which ruin the performance. Those with deep pockets could get a bank of four CR Sport carbs for about £1000 or a twin Mikuni set-up for £650. The long plastic rear mudguards got cut down and the original plastic chain guard may have gone missing by now too. Replacement mudguards carry a hefty price tag.
The original black chrome exhaust system can rot out, especially around the downpipes, and once it does there’s not a lot you can do with it. The anti-dive can just be blanked off without terrible results. The instruments can be a bit temperamental. Fairing panels are available, and you can get pattern screens, but the side panels can be harder to find and there’s a flimsy lug at the top that fractures. You will need to replace every fuel pipe, and finding the right ethanol-proof pipe is expensive and difficult but get the best you can. As long as the engine is not smoking, there are no horrible noises, and if it is not leaking oil from too many places, all should be well.
You can find them at reasonable prices too. It’s unlikely you would need to pay more than £3000, and tatty running example with a rusty Motad exhaust on it will be less than £1500. For the price of an MZ250, you could get a genuine 125mph 1980s sports tourer that will take you to the South of France in a heartbeat. GPz550s are even cheaper.
What more can you ask for? Get one now before everyone realises how good they are.
An owner’s eye view
There are a few ways of way of telling if your classic motorcycle is a classic motorcycle. Is it 40 years old? Does it have an owners’ club, or at least a model-specific social media page? Does it have at least two specialist parts suppliers, each of which regards the other in a grudgingly kindly way? If your motorcycle has books written about it, then it is a classic motorcycle.
The best way of telling if it’s a classic motorcycle, however, is, when parking it up, somebody comes up to you and says, “I had one of those.”
Sean’s GPz
It was March, and I didn’t have a bike ready for the May/June tour to Shetland. My Z650 F4 I went on in 2018 was fully stripped on my workbench and unlikely to be together and fully tested in time. My 1976 Z650 B1 was running very well, but I didn’t want to risk it. It’s great for daytripping around Somerset but not for a big tour. It is in worn, unrestored condition with minimal replacement parts to keep it running. The original single front brake disc and hose are stamped 08/76 and the tired wiring loom did not give me confidence to reliably ride up to 200 miles per day for two weeks.
I fancied a late GPz750. That’ll be perfect for me; a z650 with a bit more of everything and a half fairing. All that said, it would need to be in good nick and fit enough to tour on. Time was growing tight and there was little room for purchasing errors. My previous rolling restoration bikes have proceeded at a glacial pace despite my best intentions. Oh yeah, it had to be in Stardust Silver or even the Black version… 90% seem to be the Firecracker Red which looks great too, but I have bad luck with red bikes and cars. All my transport is either green or silver.
I found my bike on a well-known internet auction site. It was nearby, just north of Bristol, two previous owners, and £2200. This seemed reasonable for a clean, all-original bike. The seller was very private, and it took two days of messaging to convince him I was genuine and understood that he didn’t want any haggling. He was a former lecturer at a top-line public school and emigrating back to Canada in two weeks’ time. There was room in the shipping container if he didn’t get his price. Originally a Belgium market bike, he bought it from the UK importer five years ago. He only rode it 20 miles and terrified himself, had it serviced, then parked it in his living room. And there it was when I arrived first thing on a Sunday morning to a National Trust ancient house dating back to 1100 in a hamlet in the Cotswolds. All clean and shiny, unmolested by British weather, it even had the original black chrome exhaust system.
We moved it out into the rear yard, stuck an auxiliary fuel tank and a jump pack on it, and pressed go. The engine span freely but it just wouldn’t catch; 12.5 volts to each coil, clean spark plugs, head scratch. Fuel started leaking out of #3 carb. We would have happily spent another hour or so doing what we all do for fun, trying to get old bikes going, but Mr History had better things to do, so decisions had to be made. Handshakes, and Mr History even threw in a NOS Kawasaki jacket and helmet.
Three days later, my courier dropped it off straight to Dog Motorcycles for the bike’s penultimate MoT and new Bridgestone tyres. The tyres that came with the bike were 20 years old and rock hard – no wonder the bloke was terrified riding it around the narrow horse poo-covered lanes of the Cotswolds. I collected the bike a few hours later with the only advisory that ‘it goes well, but it leaks if you stop.’ I rode home without stopping. Whoever had worked on the carbs prior to storage had not tightened the float bowls. Maybe to let the last of the fuel evaporate prior to storage we’ll never know, but I wish they had put a label on them. Some of the carb screws had chewed heads and couldn’t be tightened sufficiently. Being a veteran of z650 carb removals, I wasn’t daunted about taking them off, but it proved twice as hard. The airbox doesn’t adjust backwards so there is even less room for manoeuvre. Fighting them off, sorting carbs and then fighting back on took a whole weekend.
Prior to the big trip I changed the clocks for an mph set, speedo cable and a NOS fuel tap. The fuel gauge didn’t work, which was okay for now but the red warning light on the main dash kept flashing. This was fixed with a piece of matching black electrical tape over the warning light. A few months later I found you can still buy a new Kawasaki GT750 fuel sensor which has the same tank fitting, although the float arm faces the wrong way. I managed to swap it around on the internal mounting and as if by magic, the fuel gauge worked. Ten little 1980s electrical blobs appeared on the distinctive tank-mounted display.
As I expected, riding it is like my z650 but on steroids. Same lump, but more power delivered more aggressively. The exhausts growls, it’s longer and leaner, and planted firmly on the road. I have done more than 2500 miles this summer and I love it. Nearly every time I park, sensible grown men walk up, get nostalgic, and share tales. The other day I realised that as a 1986 bike, the most modern bike I’ve ever owned. For now, I am happy in the 1980s.
Sean’s GPz just runs on and on, effortlessly. It’s as fast as he wants, solid on the road, and great for short dashes and longer runs, covering 2500 miles in just a few weeks over the summer. Over the winter he is going to take the original exhaust off and get it ceramic coated.
Is it a classic motorcycle?
Well, it is 40 years old, so the DVLC thinks so. It has specialists. And when he parks it up, people come up to him and say, “I had one of those.”
SPECIFICATION – 1984 KAWASAKI GPz750
ENGINE: 738cc, air-cooled, eight-valve, DOHC, inline-four POWER: 85bhp @ 9500rpm GEARBOX: Five-speed FINAL DRIVE: Chain FRAME: Steel-tubed double cradle SUSPENSION: Front, telescopic anti-dive forks adjustable pneumatic preload; rear, rising-rate monoshock, adjustable pneumatic preload, rebound damping BRAKES: Front, twin 280mm discs with single-piston calipers; rear, 240mm disc with single-piston caliper TYRES: Front, 110/90 x 18; rear, 130/80 x 18 SEAT HEIGHT: 800mm WHEELBASE: 1490mm DRY WEIGHT: 220kg FUEL CAPACITY: 19 litres TOP SPEED: 129mph
