USING ONE OF ONLY TWO FRAMES OF ITS KIND IN EXISTENCE AND WITH AN ULTRARARE SWINGARM AND WHEELS, MARK WATERIDGE’S GPZ REDEFINES SPECIAL.
Mark Wateridge could hardly believe his luck. Years of fruitless searching for a P&M chassis had turned up precisely nothing, and as he forlornly shuffled around the Stafford Show back in 2011 he thought he was never going to get the chance to build his dream special. “Then I saw it,” he smiles. “It was a 1984 P&M with a GSX-R750 engine in it, but when I got chatting to the guy selling the bike it became clear that he didn’t really know the finer details of what he had" Papers were promptly signed, money changed hands and over 30 years after he raced against P&Ms at club level, vowing one day to buy one, Mark finally had his own. Project P&M was on.
Well in hindsight, ‘on’ might have been a slightly optimistic word. Wanting to restore the bike to its original racing condition meant ditching the GSX-R motor and replacing it with the GPz750 engine that the frame was designed for – a job Mark thought would be routine. “I had this grand plan that all I’d need to do was take one engine out, modify a few brackets here and there and put the other one in,” he laughs. “I thought I’d do it over the winter and then it’d be ready by spring. No. Anyone who’s ever built a special will tell you it doesn’t work like that.” It certainly doesn’t.
“I thought I’d do it over the winter and then it’d be ready by spring. No. Anyone who’s ever built a special will tell you it doesn’t work like that.”
Mark duly entered a protracted four-and-a-half year period of research, discovery and patience, with the engine causing the vast majority of the head-scratching. “It started when I got hold of a GPz750 bottom end from a Uni-Trak model,” explains Mark. “I put it in and the bolts lined up on the rear mounts, but they didn’t quite fit flush to the frame sides. I phoned P&M and explained to Richard Peckett there – the guy who actually built this frame back in 1984 – that I needed some spacers for the rear mounts. “He said, ‘I can’t do that.’ I said, ‘Why not?” He explained that none of his frames had spacers on the rear mounts, which completely threw me.
**AND BREATHE...**This red device is a two-way breather valve for the fuel tank, allowing excess pressure to vent the tank but also letting in air as the fuel drops.
GOT A LIGHT? Mark wanted the Yamaha FZ750 rear light to fit flush, which took ages. “I had to cut and fibreglass a recess in the seat and make up brackets to fit the Yamaha light.”
Chain Reaction Sorting the chain alignment was a pain. I had to use a laser line tool to work out the offsets on the sprockets. Nova Racing made me a sprocket with a custom offset.”
It took me quite a while to discover that Kawasaki changed the width of the crankcases between the 1982 and ’85 GPz engines – when the later model went to the monoshock they narrowed the rear mounts on the crankcases. So I had to get an ’82 GPz750 R1 engine – the last twin-shock one which Kawasaki only did for a year. I bought it for £100 on eBay – I probably spent more on petrol driving from West Sussex to Wales and back to pick it up.”
So please tell us that went in OK, Mark? Well, nearly. “Something else I discovered was that because the frame was built for racing, you can’t put the engine in with the cylinder head on – it won’t fit,” he explains. “The head has to be off to get it in. I called Richard at P&M again and he said, ‘Yep – that’s how we designed it.’” In addition to the presence of a helpful individual who’s a goldmine of information (in this case Richard from P&M, who was always on hand to answer any of Mark’s questions), special builds almost always feature a ridiculous bargain that’s been acquired through a combination of luck and timing. In this case it occurred when Mark was ambling aimlessly through the Kempton autojumble a couple of years ago. “I wandered past this tatty stall, and stuffed between all the rubbish was this pair of valves with a bit of masking tape over them that had ‘Kwak 810’ scrawled on it in black pen. I picked them up and thought, ‘This is a Wiseco big-bore kit.’ I asked the guy how much he wanted for them plus the other six valves and the pistons, and he sucked through his teeth and said, ‘£75’. I beat him down to 60.”
With a custom-made exhaust next on the list built by Mark at MHP (“I’ve known him for years from my racing days so I knew he’d do a great job”), Mark set about sorting the bike’s bodywork. It was a bit of a mish-mash– the tank was from P&M, the fairing was from a 1989 GSX-R1100K and the seat unit was a Harris F1 number. All the parts were in decent nick, but they certainly didn’t line up and flow the way you see them now – that was all done by Mark’s fair hands.
Front End Given that a previous owner was so taken with the GSX-R1100 that he’d plonked one of its engines into the P&M frame, it’s no surprise that the entire front-end is also from the same bike – the forks, yoke, brakes, switchgear and clocks are all from an ’89 1100K model. Maxton had worked on the forks previously and Mark got them to repeat the trick with the bike under his ownership. “There are new lines, mastercylinder kit, pistons, seals, pads – it’s all been rebuilt,” says Mark.
"The seat unit needed quite a lot of fettling to look right,” he says, with a knowing smile that indicates hours of garage time was the result. “The rear light was this brick-shaped thing from a Honda CX500 Eurosport that stuck out a mile, so I got one from a 1986 Yamaha FZ750 instead and made it flush. “The fairing was from a GSX-R1100K, but I wanted to modify it quite extensively because it was a full fairing and I was after that ’80s endurance racer look. I had to cut a big chunk out and re-glass a big section of it – the 1100K fairing has two large air ducts on the side, which I wanted to make flush. I also needed to make the angle of the side of the front fairing match the angle of the seat unit, which took a while. It’s a bit OCD, but when I do a bike there’s only one way it’s going to be done – and that’s right. That’s probably why it took me four-and-a-half years...”
All specials are unique but even bearing that in mind, Mark’s is off the scale in terms of rarity. There’s the Saxon Racing ’arm and ally wheels, which Mark confesses he’s never seen come up for sale on eBay or anywhere else, not to mention the frame. “Richard told me that P&M only ever built two cantilever frames for the air-cooled 750, and mine’s one of them,” says Mark. “The other one was their own works racer from 1985, which is now in New Zealand. This is seriously rare stuff, and there’s not another bike like this on the planet – simple as that.”
You’d forgive Mark for needing to pop anti-anxiety pills every time he gets on the bike, but to his massive credit it gets used – he even battled with Big G at the PS trackday at Cadwell. “It’s just the right side of brutal, which is what an air-cooled motor with a bigbore kit and CR carbs should be,” he laughs. “Of course it’s always in the back of my mind that certain parts couldn’t be repaired, but I’ll never just put it in a warm garage and take it out once a year. It was originally designed to be used, and I’ve spent nearly five years making sure I can do exactly that.”
“The exhaust took about a year to get hold of, after I had a couple of false starts with some other companies. But I’d known Mark Hill at MHP since my club racing days and knew he’d do a great job, so I asked him to make it. I wanted to make the bike look sympathetic to its age rather than go for a kicked-up, GP-style exhaust. We liaised, Mark listened to what I wanted, told me what was and wasn’t possible and this was the result. He’s welded the header pipes but you can’t tell – what a great piece of work.”
“The bike’s had an interesting engine history,” laughs Mark. “It had a GSX-R750 motor when I got it, and a GSX-R1100 lump before that. I could see that a previous owner had modified the upper frame rails because the 1100 engine is taller. But the rear engine mounts hadn’t been changed – they were identical between the GSX-R and GPz units. I soon discovered that the same Japanese engineer had designed both engines. The fact that the P&M frame could take an 1100 engine shows just how strong it is.”
The swingarm was on the bike when Mark bought it, and just like the frame, happens to be ultra-rare. “It was made by a company called Saxon Racing in the ’80s; they made frames too, and even built one for Sir Alan Cathcart. It’s a lovely looking thing: the whole swingarm and rear shock linkage compresses the shock at both ends, whereas the original P&M set-up just had a straight, single cantilever monoshock. I’ve no idea if I could get hold of another one of these if I ended up damaging it.”
SPECIFICATION P&M KAWASAKI 750
ENGINE 1992 Kawasaki GPz750 R1, air-cooled, dohc, 8v inline-four, Wiseco 810 kit, Keihin CR31mm smoothbore carbs, skimmed and flowed head, bespoke MHP stainless steel 4-2-1 exhaust system, bespoke wiring loom.
CHASSIS 1984 P&M F1 frame, 1989 Suzuki GSX-R1100K forks, brakes, top yoke, switchgear and clocks, Saxon Racing swingarm, rear linkage and aluminium wheels, Tech 2000 rear shock, P&M fuel tank, modified GSX-R1100K fairing, Harris F1 seat unit, 1986 Yamaha FZ750 rear light
THANKS Rob at Mistral Performance (mistralperformance.com), Mark Hill at MHP (mhpexhausts.com), Tony at Cycle Sprays (cyclesprays.com), Ferret at Ferret’s Custom Electrickery for the loom (motorcyclewiring. co.uk), Richard at P&M, wife Jackie