What really set the GSX-R750 apart from other 750s in 1985 wasn’t exceptional power, but an outstanding power-to-weight ratio. The target was only a fairly moderate 73.6kW (100hp) from 750cc, but in an era where the average 750cc motorcycle weighed 220kg Suzuki aimed for a maximum weight 20 per cent lighter, at 176kg.
To achieve this Suzuki eschewed water-cooling with all its associated plumbing, preferring oil cooling, and a new acronym – SACS, or Suzuki Advanced Cooling System. The lower operating temperatures allowed by oil-cooling, compared to straight air-cooling, allowed for many lighter internal components. At 70mm x 48.7mm the engine was also extremely oversquare, with the regulatory DOHC and a four-valve cylinder head with a new version of Suzuki’s TSCC (Twin Swirl Combustion Chamber).
Feeding the cylinders were four flat-slide Mikuni 29mm carburettors, exiting through a four-into-one exhaust system, and a six-speed gearbox kept the high-revving engine on the boil. To minimise engine width the alternator was relocated from the end of the crank to the top of the crankcase behind the cylinders. Although the power was a moderate 77.5kW (104hp) at 10,500rpm, the engine unit only weighed 73kg. Unfortunately the quest for extreme lightness resulted in some components at their design limits and early engines were a little fragile, at least by Japanese standards. It is no coincidence that you rarely see an early GSX-R around these days and those that survive command a premium price.
The frame for the GSX-R750 was closely modelled on that of the works endurance racers and was the first aluminium alloy unit to appear on a mass-produced street bike. Designated MR-ALBOX (Multi-Rib Aluminium Alloy Box Section), this weighed around 8kg, but was prone to flex under racing conditions. But racetrack handling was the GSX-R’s raison d’être, and a banking angle of 55 degrees, wheelbase of 1435mm, and stout 41mm cartridge fork saw to that.
To maintain a low seat height the Suzuki Full Floater rising-rate monoshock got an eccentric cam.
The braking was also state of the art for 1985, with four-piston front brake calipers gripping 300mm discs. The rear twin-piston caliper incorporated an anti-hop torque tube. The only unexpected feature was 18in wheels front and rear. Most manufacturers at this time were experimenting with 16in wheels but as Suzuki’s endurance racers used 18in rims so did the GSX-R750. Although an 18in front wheel slowed the steering, the GSX-R made up for it with a 26-degree fork rake.
The first GSX-R750 was a milestone motorcycle, the bike that allowed everyone to share the experience of a racing bike on the street. With its emphasis on minimalism and light weight there was no more focused and affordable high performance motorcycle available at the time.
During the early 1980s, Suzuki was at the peak of its racing success. Marco Lucchinelli won the 1981 500cc title, followed by Franco Uncini in 1982. The next year saw Herve Moineau and Richard Hubin, on an air-cooled GSX 1000, win the World Endurance Championship, and this machine led to the first GSX-R.
Suzuki offered contingency money in their GSX-R cup in the US from 1986, launching the careers of future World Superbike Champions Doug Polen and Scott Russell. Doug Polen won $90,000 in contingency money in the 1986 in the American GSX-R cup.
Kevin Schwantz rode the Yoshimura Suzuki 750 for three seasons in the US, culminating in victory in the Daytona 200 in 1988.
The GSX-R750 was so successful it spawned a larger 1100 cc version for 1986. A heavily revised "Slingshot" GSX-R750 followed for 1988, but this was no longer the lithe machine of the original.
By 1992, the GSX-R750 adopted water-cooling, and for 1996 Suzuki followed everyone else by introducing an aluminium beam frame.
Get the book, Suzuki GSX-R750 Performance Projects:
This has a good Suzuki GSX-R750 history:
Check out the Gixxer forum:
Look at a range of owners’ bikes:
Great Suzuki resource:
Thanks to Allen and Lorraine Smith of the Australian Motorcycle Museum, Haigslea, Queensland, for the use of the bike featured.