Happy Birthday GSX-R750F, unveiled 40-Years ago at the IFMA Motorcycle Show in Cologne. Performance motorcycles were never the same... Photos: Heather Ware/AC Archives
Exactly 40 years ago on September 20, 1984, the unveiling of the ground-shattering Suzuki GSX-R750F at the IFMA Motorcycle Show in Cologne, Germany, saw the first streetlegal Superbike of the modern era explode onto the world stage… AC takes us through it.
The Editor on his 1985 GSX-R750F lapping The Farm. He sold this one, but has another in the garage!
Nothing about high-performance motorcycle design would ever be the same again. Ever since Honda created the four-cylinder UJM/Universal Japanese Motorcycle back in 1969 with the CB750, it’s taken turns with its three Japanese rivals to re-invent the concept. In turn, the 903cc Kawasaki Z1, the original 893cc Honda Fireblade, and the first one-litre Yamaha R1 each fundamentally changed the spirit as well as the science of sportbikes for ever with their arrival. Thereafter, all other manufacturers would have to re-evaluate their design strategies – and we, the bike-buying public, benefited enormously. Then BMW did the same in building a better, smarter J-bike with the S 1000 RR. Discuss!
Read Alan’s Throwback Thursday test on Mick Grant’s Title Winning 1985 GSX-R750F Superstock bike (above pic) here...
But no other motorcycle has taken such a huge step forwards, and in so radical a manner, as the Suzuki GSX-R750F which debuted back in the 1985 model year. Compared to its air-cooled, steel-framed, neo-vintage predecessors and those from all other companies, the oil-cooled 16-valve Gixxer (Gixer in OZ) with its GP-derived square-section tubular aluminium chassis, Full-Floater monoshock suspension, and then-improbable power-to-weight ratio, was not only the first Superbike of the modern era, it also beat the same minimalist path in concept and execution that Tadao Baba would follow eight years later in creating the first Honda Fireblade.
“Not only the first Superbike of the modern era, it also beat the same minimalist path in concept and execution that Tadao Baba would follow eight years later in creating the first Honda Fireblade.”
Yet, quite unjustly, Suzuki’s GSX-R750F project leader Etsuo Yokouchi has never been accorded the same reverential status as Baba-san for having thought outside the envelope in creating the bike that put Suzuki on the map as makers of supreme sportbikes, as demonstrated by their racetrack dominance and showroom supremacy in the wake of the GSX-R750F’s appearance just as the default capacity for such bikes was downsizing to 750cc. He and his colleagues did so by adapting various elements of Suzuki’s 500GP and TT F1/Endurance racers to production, while completely rethinking the architecture of a leading-edge sportbike.
The Black and Red sold fewer but are now of course the rarer of the two colour combinations to collect…
Under Yokouchi’s watch as chief engineer of Suzuki, the company had pointed the way ahead with the arrival of the GSX-R400 at the end of 1983, a 152kg Japan-only model whose close attention to weight saving via an aluminium frame christened MR-ALBOX by Suzuki and derived from the XR69-A World Endurance champion and XR45 GP racers’ alloy chassis, meant it weighed a remarkable 19 per cent less than its steel-framed opposition. In conceiving a 750cc equivalent for one year hence, Yokouchi set himself and his engineers a seemingly impossible pair of goals – producing 100 bhp from an all-new engine, 16 per cent more than the company’s existing air-cooled 16-valve GSX750 motor, while at the same time slashing weight significantly.
How much? Well, as revealed in Gary Pinchin’s definitive Suzuki GSX-R 750 history book (ISBN1 86126 0822), Yokouchi writing in Suzuki’s in-house Tech News magazine reasoned that if they’d saved 19 per cent on the GSX-R400, then the new 750 should be 20 per cent lighter than anything in its sector. With the average weight of Suzuki’s rivals at 220kg, that meant the new bike had to weigh no more than 176kg with all street equipment – a respectable weight even nowadays, but a pipedream back then at a time when Honda’s new 86bhp VF750F Interceptor scaled 221kg dry, and Suzuki’s own class-leading GS1000, the lightest and best-handling of all the one-litre fours, was marketed as “the lightweight heavyweight”! Yes, really….
An all-new engine was obviously required, and designer Tansunobu Fuji brought blue sky thinking to the project by opting for an oil-cooled design, rather than a heavier water-cooled or less efficient air-cooled format. Suzuki’s turbocharged 650cc XN85 model had pioneered the use of oil jets to cool the underside of the pistons, and Fuji extended the idea to the GSX-R750 motor, thus saving significant weight by eliminating the need for a water radiator and cylinder jackets. A large-capacity double-chamber oil pump ensured the five litres of combined coolant and engine lubricant ran cooler, thus extending oil life and allowing higher rpm, plus a reduction in the weight of conrods, pistons and crank, thanks to lower operating temperatures.
Suzuki called what was effectively an oil-assisted air-cooled format the Suzuki Advanced Cooling System/SACS
Suzuki called what was effectively an oil-assisted air-cooled format the Suzuki Advanced Cooling System/SACS, and this feature was the single greatest step forward in meeting the company’s ambitious design targets, as noted by Tech News in comparing the weights of individual components in the new engine versus the old. Compared to the previous air-cooled GSX750, its oil-cooled successor’s piston was 11 per cent less in weight, the conrod 25 per cent, the crank 19 per cent, the cast magnesium cylinder head – the first time this material had ever been used on a production engine’s head – 22 per cent, and the cylinder block 17 per cent.
The 70 x 48.7 mm short-stroke 749cc motor weighing just 73kg (compared to the 80kg 747cc GSX750’s 67 x 53mm format) had four valves per cylinder operated by twin overhead camshafts with central chain cam drive. It featured an evolved version of the TSCC/Twin Swirl Combustion Chamber format first seen in 1980 on the GS1000, which took advantage of the turbulence caused by the incoming fuel charge to increase airflow and enhance flame passage, en route to a claimed output of 104.5 bhp at 10,500 rpm at the crankshaft.
This entire layout was revolutionary in its format…
The 26mm intake and 24mm exhaust valves sat at an included angle of 21°, fed by Mikuni VM29SS flatslide carbs breathing from a large eight-litre airbox located under the fuel tank. A six-speed gearbox was matched to a hydraulic clutch, rather than the then-commonplace five-speed transmission with cable clutch. And rather than hanging the generator on the end of the crank as was hitherto commonplace, thus reducing ground clearance and lean angle, Suzuki relocated it behind the cylinder block above the gearbox, driven by a spur gear. Reducing the width of the engine in this way allowed a potential 55° banking angle, far more than the competition. This entire layout was revolutionary in its format – many of the Gixxer’s design components that we now take for granted in performance engineering were pioneered on this bike.
The same applied to the chassis in which this literally revolutionary engine was located, and by following the example of the GSX-R400, frame designer Takayoshi Suzuki permitted the team to deliver a motorcycle that indeed weighed a scant claimed 176.4kg dry when the GSX-R750 was unveiled at the Cologne Show in Germany in October 1984 – a remarkable 44kg lighter than the less powerful GSX750 it replaced, and 36kg less than its rival steel-framed 20-valve Yamaha FZ750, whose arrival deadheated with the Suzuki. To do this, he adopted a then-unique square-section tubular aluminium frame, a duplex cradle design like the racers which spawned it, which while as strong as the steel frame it replaced was far lighter, weighing just 8.1kg – less than half that of the GSX750’s steel chassis.
A remarkable 44kg lighter than the less powerful GSX750 it replaced, and 36kg less than its rival steel-framed 20-valve Yamaha FZ750″…
“The primary method used by the team was to reduce the aggregate number of components in the frame.” Suzuki-san wrote in Tech News. “By doing this, the number of welds reduced correspondingly. Fewer welds mean lower weight, and offer the additional advantage of reducing labour costs.” So, as the first aluminium streetbike chassis to enter volume production, the GSX-R750 frame was a modular design comprising five alloy castings either welded or riveted to a total of 21 sections of extruded box-section aluminium tubing, compared to no less than 96 components of its GSX750 predecessor’s steel chassis. Slim, tall and short, the new Suzuki had a tight 1405mm wheelbase – much shorter than its rivals, with the Honda VF750F’s 1495mm stride and 1490mm for the new Yamaha FZ750, practically truck-like by comparison. Compared to them, the new Suzuki seemed a three-quarter scale model, especially with the rider aboard ensconced in the low 765mm-high seat, compared to the then-typical 790mm lift of the FZ750.
1985 Suzuki GSX-R750F engine
Thanks to their lighter materials and rationalised internal design, Suzuki didn’t give any of that savings back again by upsizing the cartridge forks to 41mm in diameter from 37mm on the GSX750, matched to a redesigned Full-Floater monoshock rear comprising 35 per cent fewer parts mounted on a box-section aluminium swingarm. These carried 18in wheels rather than the 16in rims then briefly becoming fashionable, with 300mm front discs gripped by four-piston Tokico calipers. With hollow chrome-moly axles, lighter low-profile Bridgestone rubber, spirally-drilled brake rotors, aluminium triple-clamps etc. etc., Suzuki made sure its suppliers all came to the party in terms of saving weight – and the result was a truly ground-breaking motorcycle, the first sportbike of the modern era, which entered production exactly 40 years ago this year. Happy 40th birthday, Gixxer – performance motorcycles were never the same after you got born.
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