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Project GPZ900R

Published: 25 December 2015

Updated: 27 November 2015

Kawasaki’s GPZ900R was a sportsbike masterpiece when it was released in 1984, but it’s still possible to improve the design further. So when Ian Broadfoot restored his A1 to original condition, he took the opportunity to address the 900R’s little flaws and make it even better

 

hen the GPZ900R’s rakish face made its first appearance in UK Kawasaki dealers, Ian Broadfoot was running around on an altogether less-advanced Yamaha RD250LC. Like countless others of his generation, he was astounded by Kawasaki’s new superbike creation, but had neither the financial means nor the courage to step up to the big GPZ.

“When I first saw the 900R, I could never afford one, but I fell in love with it anyway. I had to stick to my 250LC. A guy named George I knew bought one, and I was so jealous. I think he wrote it off a few months later, and I never had a go on it – I wasn’t brave enough.”

The usual story of house buying, getting married and having kids put paid to Ian’s biking for many years after that, but the impression the GPZ made on him stayed with him. When he decided to get back on two wheels in 2007, there was only one machine on Ian’s shopping list.

“I started trawling everywhere – eBay, Gumtree and so on – for an A1, and I eventually found this one for sale in Derby. So I made some phone calls about the bike and came to the decision to get it.

“It was painted blue with airbrushed graphics and had a different exhaust, but apart from that it was original and hadn’t been abused. Little things like the sidepanels had all the lugs – it’s hard to find one that hasn’t been broken, because they have to be removed in a certain way so they don’t snap. Things like that make the difference.

“I’d been offered other bikes when I was hunting – but none of them ticked the right boxes for me. They weren’t right or they were later models.”

Ian spent the rest of the summer riding the GPZ as it was, to get a feel for it and to get back into bikes. When the misery of a Scottish winter closed in, the GPZ came off the road and onto the workbench for a cosmetic overhaul.

The paintwork was a key consideration in Ian’s restoration – although well finished and not unpleasant in design, it was far from the simplistic beauty of the red/gunmetal scheme only used for the A1.

GS Chapman Vehicle Body Repair in Lamancha in the Scottish Borders were entrusted with the 900R’s panels. They’re predominantly a car repair business, but they were recommended to Ian for bike work and have since done more GPZs.

Ian sourced his decals from the The GPZ Zone, which predictably is a business dedicated to keeping 900Rs (and the 500S for that matter) on the road. They’re perfect reproductions of the original logos, down to the blue ‘R’, ‘DOHC’ and ‘Valve’ on the sidepanels, unique to the A1.

Ian credits the Zone and the forum members on the same site as a big help in the project. “There’s so much information on there – it doesn’t matter what you’re thinking about doing, there is someone who knows everything about it, or people who can help.”

With the panels off, the state of the bike underneath was evident. The GPZ had fared pretty well, with under 30,000 miles on the clock and evidence of caring previous owners, but the compact packaging meant some areas hadn’t seen the friendly touch of a cleaning brush in many years.

The engine was removed from the chassis and given a makeover. The head and barrels were painted in satin PJ1, and the clutch, pulser cover, cam cover and front sprocket covers were treated to a resilient powdercoat.

The front of the engine took the most attention. The fairing and radiator make access and even inspection impossible. With the bike in pieces, Ian could see the GPZ needed some help.

“It already had single-skin stainless header pipes and a collector box, which just needed a clean and paint. But there’s a steel water manifold on the front of the engine which can rot through. A new one is £80, and then you need the seals.

“You have to be so careful fitting it – it has to go in square and without the seals catching and rolling. The only way you can test them is fitting the engine back togther and running it – if you’ve done it wrong and it leaks, it means stripping it again.”

Thankfully, Ian’s replacement went in without a problem. The rest of the cooling system was fettled too – a notorious issue with GPZs. Early bikes can overheat, partially due to the compact packaging, partially due to an inefficient design.

A manual override switch for the cooling fan is the simple remedy, allowing the rider to prevent overheating before it happens, and while Ian’s bike has one, he’s gone further with solving the issue.

Upgrading the radiator cap from 0.9 bar as standard, to a 1.1 bar cap helps matters, and a full set of black silicone hoses, which help with heat dissipation, are fitted too.

The original plastic cooling fan had suffered from the increased heat given off by the single-skin header pipes, and had suffered melted tips. The solution is an aluminium fan blade on the original fan unit (which Ian had blasted and powdercoated too) from Muzzys, who also claim improved cooling effect from the fan design. The radiator itself wasn’t in bad shape; careful cleaning and straightening of the fins with feeler gauges saw it right.

The chassis was also in reasonable condition, but with fresh bodywork waiting to go on it needed some work. All the fairing and ancillary brackets were blasted and powdercoated, as was the aluminium rear section of the frame.

The main diamond frame got a different treatment, as Ian explains. “I debated getting it done, but I didn’t want to lose the frame numbers underneath it. Some people have had it done and it’s been OK, but I’m still on the fence about it, so I did it with gloss-black Plasti-Kote myself. It’s a good finish, and it’s all hidden anyway, so it’s not a problem.

GS Chapman were also tasked with painting the black wheel centres, and the polished rims and spokes details were buffed by Ian himself, as were the footrest plates.

The whole chassis was treated to new bearings to keep the handling nice and tight – the bike had been sat for a while before Ian picked it up, and the head bearings had left an imprint on their races, which caused a slight shimmy as the steering fought to settle in position. Not ideal with 155mph potential.

The single-piston brakes need to be in top condition to stop 228kg of Kawasaki, so Ian cleaned and check the pistons, and fitted new genuine seals from the GPZ Zone.

The anti-dive mechanism isn’t designed to be rebuildable, but again the GPZ Zone came to the rescue. Site founder Craig Davies offers a kit of overhaul parts he’s sourced to restore the anti-dive where Kawasaki won’t supply parts, and it’s this that Ian sorted his front end with. New fork oil seals were fitted – it’s since needed another set, but they’re holding up for the moment.

Ian also fitted a set of new airbox-to-carb rubbers – the cause of many a skinned knuckle and curse uttered, as getting a proper seal with four age-hardened rubbers at once is a swine.

Ian’s A1 had the common Motad Neta silencers in place of the long-since rotted originals. They’re an acceptable aftermarket replacement, but they don’t look right. New Kawasaki parts are expensive, however. The happy medium is a set of Italian-made Sito silencers, which replicate the originals in design and finish. Mated with the stainless headers and mid-section, they not only look the part, but also give the advanced dohc motor a subtle deep-throated growl. Concours anoraks won’t approve, but it’s a bike Ian built to ride, not polish.

And ride it he has. With the bike in one piece, Ian completed 2000 happy miles around his native Scotland. But the Kawasaki soon needed to come apart again when, a couple miles from home, trouble struck.

“It started running really rough and feeling like a tractor. It had thrown the big-end shells on cylinder three – the GPZ’s oil feed lubricates that cylinder last, so if oil pressure is a bit low, it doesn’t get enough oil.

“The solution is replacing the original pressure-relief valve, which is a spring-type and fatigues over the years, with one from a ZZ-R1100. It’s a piston-type, bolts straight on and is more reliable.”

The sick motor was repaired with another second-hand crank Ian sourced – not a straightforward task, as there are different grades of crankshaft and you need to replace like-for-like. Brand-new shells were fitted to stave off any chance of another failure.

While the bottom-end was in pieces, Ian took the chance to make further retro-fit improvements from later Kawasakis.

“The thing you have to remember is the A1 was the first year this engine was used, and although it’s a good engine there’s a few things they improved in later years.”

A common GPZ weak spot is the starter clutch, which can crack and fail to engage properly. The solution is replacing the standard three-pin component with the six-pin item from a ZZ-R1100.

Kawasaki helpfully retained basic engine architecture right up to the ZZ-R1200, so the part is a direct fit – you just need the matching idler gear for it to mesh properly. Ian paid around £40 for used parts, whereas a replacement 900R assembly is £130. A no-brainer, though it can only be done with the engine cases split.

The pistons and bores were fine, so went back in. A new camchain went in and its tensioner was replaced, again with ZZ-R1100 parts. The ratchet-type adjuster doesn’t suffer the same age-related fatigue as the sprung original, giving more peace of mind.

The cylinder head was also in good shape, though Ian took the opportunity to regrind the valves and fit new seals while it was off, ensuring the top-end will be good for tens of thousands of miles to come.

Another simple trick learned from the owners’ forum is the fitment of a four-degree ignition advancer place. The switch from the leaded fuels the GPZ would have orginally slurped down to modern unleaded allows the ignition to be advanced a touch, giving a crisper response. It’s a £20 bolt-on mod, available through gpzzone.co.uk forum member ‘Mr P’.

Since the engine rebuild, the Kawasaki has been back on the roads of the Highlands. It’s not Ian’s daily transport, and a family means he can’t get out every weekend, but when the GPZ does get wheeled out, he makes the most of it.

The active and sociable GPZ owner community regularly meets, and Ian’s sorted Kwak regularly beats a path to the Isle of Skye in the north, and down south to the English Lake District to talk Gee-Pee-Zed with fellow owners.

Now as then, the GPZ900R is a handy tourer as well as a fantastically rapid sportsbike, though Ian has made a couple of changes to improve the Kawasaki’s long-haul comfort capabilities.

A set of Nonfango hard panniers, topbox and luggage rack are fitted for longer outings, and a more supportive seat is fitted in place of the original, which doesn’t give the support it once did after a few hours on the road. Both are removed for general riding duties though – it wouldn’t be fair to ruin the GPZ’s sleek shape on a permanent basis.

So, 27 years since he first lusted after a 900R, is Ian happy with his restored superbike? Of course he is.

“I’m really please with how it’s turned out. Even just opening the shed door puts a smile on your face, and when you’re going up through Glencoe on it, there’s nothing better. There’s nothing more I need to do with it, it’s just upkeep from here on. I’ll strip the brakes and anti-dive to check them this winter, but apart from that there’s nothing more to do.”

 

Words Chris Newbigging  Photography Mark Manning

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