Collectible: 1985 Suzuki GSX-R750

The introduction of the Suzuki GSX-R750 marked a turning point, offering for the first time a street-legal Japanese motorcycle capable of race-bike performance…

“A Legend Now Begins” was how Suzuki’s publicity heralded the introduction of the GSX-R750 Hyper Sports in 1985, and for once the publicists got it right. Few motorcycles have emulated the impact of the GSX-R750, a motorcycle that has set a benchmark for affordable production sporting motorcycles for decades. Before the GSX-R there were no real racing-derived street Japanese motorcycles. Although the Japanese had ruled the racetracks for more than 20 years, somehow this didn’t translate into production machines.

During the 1970s the Japanese couldn’t see why street motorcycles needed clip-on handlebars and rear-set footpegs. Although the Italians were adept at producing expensive limited-edition production racers, the GSX-R750 was the first widely available race replica motorcycle since BSA’s Gold Star of the 1950s and early 1960s.

For the first time in two decades here was a motorcycle the average punter could ride at the track and ride home afterwards. As the first pure race replica from the Land of the Rising Sun, the GSX-R750 also created a subculture that continues today.

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 carburetors, 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 104hp (77.5kW) 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 18-inch wheels front and rear. Most manufacturers at this time were experimenting with 16-inch wheels but as Suzuki’s endurance racers used 18-inch rims so did the GSX-R750. Although an 18-inch 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.

Thanks to Allen and Lorraine Smith of the Australian Motorcycle Museum, Haigslea (Qld) for the use of the bike featured.

THE VALUE PROPOSITION

These are the numbers you’ll need to crunch to put a Suzuki GSX-R750 in your own shed…

Original price tag for a SuzukiGSX-R750: $5495
Current valuation for one in average condition: $5500
Current valuation for one in mint condition: $10,000+

FAST FACTS

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 its 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.

WANT TO KNOW MORE?

Get the book, Suzuki GSX-R750 Performance Projects -- www.pitstop.net.au/view/products/page/query/plu/13853
This has a good Suzuki GSX-R750 history -- www.pitstop.net.au/view/products/page/query/plu/12383
Check out the Gixxer forum -- www.gixxer.com
Look at a range of owners’ bikes -- www.bikepics.com/suzuki/gsxr750

Story courtesy of Motorcycle Trader

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Collectible: 1985 Suzuki GSX-R750

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