Nearly 40 years ago the GSXR 750 came out in 1985.
Unleaded fuel became mandatory in 1986 the GSXR had to be detuned the 1985 model was faster.
At 176 Kg it was around 30 kg heavier than RD250 i had.
1985 GSX-R750 review: A legendary superbike
So let's set the context: it's the early 1980s. Your name is Etsuo Yokouchi, you work for Suzuki in the engine design department, and you’ve just been told to produce, from scratch, a completely new kind of 750 sports motorcycle. One that will, straight out of the box, destroy the opposition not just on the street but also on the racetrack.
Wow. Er, OK.
Early '80s sports machines were heavy and wallowy. In the preceding ten years, Honda and Kawasaki had been battling for the performance crown. Honda started the power wars off with its 68bhp CB750. Kawasaki’s 900cc Z1 of 1973 raised the bar to 81bhp. By 1978, Suzuki fans had their own superbike, the 90bhp GS1000.
Yokouchi told his crew to build him a 750 engine that would deliver 100bhp and 146mph. That may not seem a lot for a 750 today, but in the early 1980s when the development of the GSX-R began, it was off the scale. The engineers were given carte blanche to change anything and everything. That meant a radical new look at both engine and chassis design and an even more radical look at weight saving.
Eventually Suzuki’s engineers came through with an uncompromising but also reliable motor featuring 29mm flat-slide carbs, some magnesium components, and a 100bhp+ output. All the engine parts had been optimised not just for weight but also for durability.
The motor was successfully dyno tested, screaming hard on the redline for a full 24 hours without breakage. In works racer spec it could go to 130bhp.Getting rid of engine heat had been Yokouchi’s team’s biggest challenge. Remember that engines were still air-cooled at the time. Chucking on a full watercooling system would have boosted reliability but would also have added around 10% more weight to the engine package.
The solution they came up was ingenious: better air cooling combined with a separate oil cooling setup for the top half of the engine. They called it SACS – Suzuki Advanced Cooling System. The SACS system delivered watercooling levels of heat dissipation without the weight penalty.
Out went the old GSX750’s tubular steel cradle frame, which tipped the scales at nearly 40 pounds. In its place came a box-section aluminium MR-ALBOX chassis with a minimal amount of welding. It was so light – just 17 pounds – that the Hamamatsu line workers at the factory could easily pick them up with one hand.
The twin-headlamp fairing and seat unit had no unnecessary curves. The bike’s flat and utterly functional look made it the nearest thing to an endurance racer yet, and gave rise to the ‘slabside’ nickname.
The ‘racer on the road’ thing wasn’t just a look. It was real. The clocks mounted in foam, the braced 41mm forks, the tank breather tube and flip-back filler cap, the 18in wheels specified to ease the lives of endurance race teams when just about every other road bike had 17s – it was all real.
The whole shebang weighed in at 176kg in US spec and 179kg for the Japanese domestic market version. That was a staggering 20% cut on the norm for the 750 class at the time.
The GSX-R 750F was shown at the 1984 Cologne bike show and put on sale in March 1985 at a temptingly affordable price. I was working for SuperBike magazine at the time, and can still remember the seismic impact it had on sports motorcycling. The visual promise was fully backed by reality, too. Not just on the road where, if you likened previous 750s to a thrush or a sparrow, the GSX-R was a humming-bird – fast, darty, super-light, and hugely responsive – but also on the world’s great racetracks. On its world endurance debut, the Le Mans 24 Hours, it came first and second – an unbelievable result.
Subsequent GSX-Rs became more rounded and generally softer as dull economics and the need to think about the bottom line got in the way of specialisation.
The first GSX-R750 (it was sold as a 400 in 1984 in Japan) was incredibly light at 176kg with sophisticated suspension and race-ready brakes. Oh yes, and it came with drop-dead gorgeous racer styling, to all intents looking like a factory endurance racer, and finished in factory colours to boot.
In 1985 there was nothing sexier.
https://www.visordown.com/reviews/motorbike/1985-gsx-r750-review 
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