From the left-field

This is a motorcycle that used monocoque thinking to perform in a very special way indeed.

At a time when avant-garde thinking was (arguably) around more than in current racing circles, there was a plethora of frame and chassis designs doing the rounds. Dave Hiscock's Coleman Suzuki is worth a close-up look from the period. Like this.

Monocoque-framed bikes – in which the fuel is carried within the chassis, not in a separate tank – have been the next big thing for more than half a century, ever since the 250cc Eduardo Giró-designed Ossa made its GP debut in 1968 in the hands of Santiago Herrero. Despite its rotary-valve single-cylinder motor producing far less power than the multi-cylinder Japanese and Italian bikes ranged against it, the lightweight Spanish-built single won four GP races and led the world championship going into the 1970 Isle of MANTT, where Herrero sadly lost his life at the circuit where he’d finished third on the bike the year before. Ossa retired from racing immediately – but the monocoque cause was taken up soon after by French engineer Eric Offenstadt with his Kawasaki-powered 500/750cc bikes, then eventually a decade later by the Japanese factory itself with the KR500 GP machines raced by Kork Ballington and Gregg Hansford in 1981-83 alongside Giancarlo Morbidelli’s 500GP squarefour. In between, Peter Williams had won the 1973 Isle of Man F750TT on his John Player Norton Monocoque, only for this to be dropped in favour of a conventional but inferior (because heavier, and less rational) albeit more accessible spaceframe design for the following season. And of course Honda used a monocoque

chassis for its oval-piston NR500, but the least said about that the better… The JPN Monocoque is widely considered to be the most successful such bike yet built – but history books show that it was nothing of the kind. That honour instead goes to a motorcycle constructed far away from Europe and even Japan, then the joint epicentres of motorcycle design. The Coleman Suzuki GS1000R whose aluminium monocoque frame was built in New Zealand by British expat Steve Roberts, took Kiwi rider Dave Hiscock to third place in the 1982TT Formula 1 World Championship, third again in the British TT F1 title race that same year – competing in both against the factory Honda and Suzuki teams – and then to victory in the end-of-season Swann Series championship in Australia, ranged against 500GP bikes with a superior power to weight ratio than the four-cylinder ‘diesel’ Monocoque. No contest. Hertfordshire-born Roberts began working with aluminium as an apprentice at De Havilland Aircraft, before joining Aston Martin for a year to hand-build DB4S. In 1962 he and wife Pam emigrated to New Zealand, where Steve ended up as a panel beating tutor at Wellington Poly. A keen off-road rider back in the UK, he couldn’t afford such a bike in NZ unless he built it himself, so he made his first semi-monocoquetriumph-engined MX bike which he named the Spartan, whose fuel tank, airbox, seat and rear mudguard were formed from a single piece of glass fibre, albeit atop a steel frame. It worked so well that in 1967 he began making Spartan-triumphs for customers. But it wasn’t until after he’d got involved in building replica Suzuki TR500 road racers between 1969-74 that Steve Roberts began building ‘proper’ monocoques. Soon after his arrival in NZ Roberts had got to know Juniortt winner and former AJS factory rider Rod Coleman – the leading Kiwi GP road racer of the 1950s – who on returning home had teamed up with his brother Bob to become Suzuki’s NZ importer. Through a mixture of astuteness, drive and hard work the Colemans built Suzuki into the No.1 best-selling brand in NZ, and Rod inevitably wanted to go road racing to promote the make with the newtr500 paralleltwin launched in 1968. But the reduced number of import licences available for individual bikes meant that they couldn’t afford to ‘waste’ any to import a built-up road racer, when there was so much customer demand for roadbikes – though spare parts were no problem. So when Malaysian rider Sonny Soh crashed his works-suppliedtr500 Suzuki at Shah Alam in 1969 and bent the frame, it was sent to New Zealand for Steve Roberts to repair – but while doing so, he made a jig and constructed an identical copy, which he then improved by fitting tapered roller steering head bearings, and a stiffer swingarm made from square s section tubing running on needle rollers. Rod then financed the production of a series of o TR500 replicas built by Roberts with Ceriani suspension s and Oldani brakes, often with slightly different d steering geometry. After Rod had negotiated n with Suzuki for the special parts needed t o convert standardt500 road engines intotr500s, t hese ended up faster than the factory originals, t hanks to special multi-port barrels developed by Wellington W Suzuki tuner Dick Lawton. Riding just such a Roberts-built replica TR500, NZ’S N Keithturner finished second behind the in nevitable Agostini/mv combo in the 1971 500cc world w championship, including three second places, p while fellow Kiwi Geoff Perry rode his Roberts-framed R Suzukitr500 to victory in the 1971 Singapore S and Malaysian GPS, and the NZTT. In the 1972 1 Daytona 200 Perry was set for victory on the Roberts-framedtr500 R when the drive chain broke on o the very last lap. Altogether, Steve Roberts built 20 tubular steel chassis for the TR500 engine, whose riders also

included Ginger Molloy, Pat Hennen, Warren Willing and Dale Wylie and sent two such frames to Heron Suzuki in the UK for Barry Sheene. And then he built his first Monocoque version…

Time to apply the thinking

During the 1971 GP season Keith Turner had become good friends with French rival Eric Offenstadt, and had plenty of chance to observe from close quarters how well Eric’s monocoqueframe Kawasaki H1R handled. On his return to NZ that year he showed Steve Roberts photos of the bike, and asked him to build a Suzuki powered version which Turner took to test at the Levin circuit, finding that it handled even better than his Roberts-built tube frame bike. But the frame shrouded the air-cooled motor, and although in Europe the TR500 monocoque was a flyer when it was cold, Turner stopped to race in the Singapore GP en route to Europe where it overheated and lost power thanks to hot air feeding the carbs. So the project was abandoned, and not revived when the liquidcooled Suzuki XR 05 motor appeared a year later. That same year, 1972, saw Wellington-based Dave Hiscock and elder brother Neville begin racing on Norton Commando 750s on the Gracefield street circuit in their home suburb of Lower Hutt. Sponsored by Coleman Suzuki, Dave Hiscock went on to dominate the big-bike Production class in Australia and New Zealand in the 1970s and early 80s, gaining 40 consecutive race victories on Suzuki GS1000 and GSX1100 bikes in the course of just two seasons. He won the NZ Castrol Six-hour race five times, including teaming with brother Neville to win in 1982 on a Suzuki GSX1100 Katana on his return to New Zealand after his debut season in the UK in 1981. There, Dave had finished second to Honda Britain’s works rider Ron Haslam (CB1100R) in the 1981 British Streetbike Series on a GSX1100, and eighth in the British TT F1 series on his Kiwi-framed Mcintosh-suzuki (on which he’d won back-to-back NZ Open class titles) behind newly crowned TT F1 World champion, fellow-kiwi Graeme Crosby’s works XR69 Suzuki. Plus, on his Isle of MANTT debut Dave Hiscock finished 14th in the F1 race riding an older XR69 loaned by Heron Suzuki. This ride convinced Dave that he needed a bike with the XR69’S quicker yet stable steering, rather than the heavier handling Mcintosh, so on his return to NZ he sought out Steve Roberts to ask him to build him such a bike. When Roberts suggested a monocoque-framed TT F1 bike would get him more readily noticed and perhaps lead to some factory support, Hiscock agreed, so after first visiting the nearby Southland Museum where Croz’s world champion XR69 was conveniently on display to measure up its geometry, Steve and his teenage son Ralph began work on the bike in January 1982, which was financed by Coleman Suzuki.

The technical bits start

The aluminium monocoque frame that resulted was entirely gas-welded by Roberts using 3mm wall thickness material, with distinct, flowing Katana-esque lines. The one-piece chassis incorporated the steering head, the 24-litre fuel tank internally braced for extra rigidity and lined with a rubber diaphragm, and the vertical plates for the swingarm pivot and rear engine mounting bolts plus it used the Yoshimura-tuned GS1000R motor supplied via the Colemans as a stressed member. There were just two mounting bosses each side for the motor, each fitted with steel inserts – engine changes took just 20 minutes. The beefy 38mm Kayaba fork originally fitted sourced from a Katana GSX1100 and set at a 24.5º rake with 90mm trail, featured adjustable air damping and hydraulic anti-dive. But once Hiscock started to do well on the bike, Heron Suzuki loaned him a works Kayaba front end from their exMamola Suzuki RGB500.THIS included magnesium triple clamps and factory brake discs and calipers, which he used for the second half of the season and for the Swann Series. At the rear, Roberts’ own interpretation of Suzuki’s trademark Full Floater suspension was fitted with a Kayaba shock, after he couldn’t get the link based on the dimensions provided by Heron Suzuki to work. So close was Roberts’ final design that someone attached Suzuki Full Floater stickers

to the swingarm while the bike was in Europe. To address the hot air problems encountered on thetr500 monocoque, Roberts consulted with NZ’S Leda Formula 5000 racing car builder Graham Mcrae and on his recommendation fitted a still-air box surrounding the four 33mm Mikuni VM smoothbore carbs, fed by twin air ducts positioned in the seat to draw air from the area behind the rider. Once connected, these worked so well that Hiscock reckoned they gave an extra 5bhp, provided any air leaks were carefully taped up. However, when he came in from a race, the first thing he had to do was cover up the open inlet ducts by stuffing rags down them, since otherwise people would throw stones down them. Really. Despite the entire motorcycle being built in Roberts’ workshop on his farm outside Wanganui, the Suzuki Monocoque first ran just six weeks after Steve first picked up his welding torch. The engine was an eight-valveyoshimura-tuned GS1000R producing 134bhp at 10,000rpm (at the gearbox, as raced) running an 11.8:1 compression ratio, with 76ft-lb of torque at 8,000rpm. To save weight without fitting a battery, ignition was provided by a Bendix-scintilla magneto with platinum points and dual ignition, neatly fitted where the old starter motor was housed, with typical high quality Roberts made covers to the toothed belt drive. This resulted in a bike weighing 159kg dry, split 49/51% rearwards. Transmission was a close-ratio five-speedyoshi gearbox with a 15-plate oil-bath clutch, and with Rix Fairings bodywork the bike was timed at 183mph in the 1982 IOMTT – albeit inevitably slower than the more powerful factory XR69 Suzuki’s 190 mph top speed. Once completed, the Monocoque Suzuki was ridden up and down the country road outside Roberts’ Brunswick farm by Hiscock. “He was away about 10 minutes, but I could hear him for miles and boy, it was fantastic!” said Roberts. “I’m

Fairing off and you can see just how narrow a front the design gave. Steering damper is essential.

The author on track with the Suzuki. Alan’s not a very tall chap so you can see just how small a bike this is.

Look at how small the mid-point is with the chassis design. You sit both in and on this bike.

Sculpted knee slots ensure little interference from wind at high speeds.

Neat flared underseat was interesting aero at work.

Mostly motor. As you'd expect.

The underseat routing is a solid idea.

Stubby race exhaust before stubby race exhausts were popular.

Testing and racing miles leave their mark.

A shame that the downpipes of the GS dominate the unfared look so much. But there's nothing that could have been done about that.