Half A Century Of Haze!
Classic Motorcycle Mechanics|November 2020
Suzuki’s GT750 two-stroke triple was the factory’s first real superbike. John Nutting details its origins and rides two examples of a machine with a faithful following.
John Nutting

With 50 years having passed since Suzuki’s two-stroke GT750 was launched, it’s easy for many motorcycle fans these days to regard the bike as a bit of a dinosaur, a smoking throwback from an era of unbridled and eventually doomed excess.

But at the time, we could hardly believe what we saw in the papers after the T750R, as it was then known, was unveiled at the 17th Tokyo Show in October 1970. In the 1960s, Japanese two-strokes meant performance, but large-capacity two-strokes were just a dream.

Kawasaki was first to translate that into reality with its Mach III in 1969. Despite being 500cc, the Mach III’s almost unbelievable acceleration was more than a match for Honda’s CB750 four, BSA-Triumph’s 750cc triple and Norton’s Commando twin, all four-strokes. Surely then the Suzuki T750R, the first liquid-cooled superbike, would be even more phenomenal.

Top of the range from the Hamamatsu factory had until then been the 500cc Cobra, a bigger version of its air-cooled twins: with an extra cylinder, the T750R offered much more, with speculation that 75bhp would be possible, offering a top speed of more than 125mph. Few technical details were available, and Suzuki wasn’t even confirming that the bike would go into production.

Development continued and later in 1970 Suzuki invited dealers to see it first hand in the US and Europe. After appearing in Germany, the first bike in the UK arrived on Christmas Day 1970 in readiness for January’s Olympia Motorcycle Show. Even then the bike didn’t go on sale outside of Japan in 1971. More improvements were made and the first opportunity for journalists to ride the machine, now called the GT750, was in California at the end of the year.

The GT750 was a Grand Tourer – as its title suggested – with smooth flexibility and a modest top speed in the region of 110mph, not a Kawasaki beater. So what was Suzuki’s management thinking when they conceived the bike?

Ray Battersby, who worked at Suzuki GB in the 1970s and is author of the definitive book about the factory’s racing machines, used his contacts to find out how the bike evolved. Suzuki’s president Jitsujirou Suzuki had called for the ‘ultimate two-stroke big bike’ to compete with Honda’s CB750 four, even if it was thought that anything larger than 500cc was impractical.

“When the specifications were revealed it was clear that the Suzuki was indeed a 'Grand Tourer' as the name suggested and not some fire-breathing Kawasaki triple beater...”

But general manager Masanao Shimizu was confident that by employing liquid-cooling, which had been used on the racers, a 750cc two-stroke could be developed. Requirements for the GT750 were that the peak power should be 67bhp, the same as the CB750, with a flat torque curve and top speed of 180kph (112mph) and a low-frequency exhaust note, because people didn’t like screeching two-strokes. The bike should have low mechanical noise, especially the transmission, offer durability, and have high-speed stability for US freeways.

Engine design was the responsibility of Seiichi Suzuki (no relation to the company president), who had been familiar with liquid-cooling, but he realised that there were new challenges with a three-cylinder machine. The first was reducing the width across the cylinders. This was reduced by rotating the transfer ports so they overlapped. The width across the gearbox was also reduced by taking the primary drive from between the two right-hand cylinders. As a safety move, much of the coolant piping was included with the engine castings, but Shimizu faced leakage problems that were eventually overcome.

Shimizu was succeeded as race manager by colleague Etsuo Yokouchi, who was involved with the GT750 project after its launch to improve the bike’s performance and handling to satisfy riders in Europe. Yokouchi visited Europe in the autumn of 1973 to hear what the dealers and distributors had to say about the GT750. “Most GT750 buyers wanted more power and a better lean angle; the exhaust and centre stand were scraping the Tarmac too soon. Back in Japan he made the changes that were introduced on the GT750L in August 1974,” said Battersby. Yokouchi went on to take charge of testing the GS four-strokes in Europe and developing the GSX-R series.

Maurice Knight, who was sales director at Suzuki GB when the GT750 was launched, recalls that development had already been almost completed when he first saw the bike at the Hamamatsu factory in 1970. “When we took over the importing of Suzukis (by Lambretta-Trojan from Associated Motorcycles in 1969) there was already a range of machines up to 500cc,” he said. “The GT750 was a new item and we had nothing to do with what it would look like.”

Knight was invited to Japan with Suzuki GB managing director Peter Agg to see the new superbike. “It was presented to us as a package at the test track. And although we didn’t have any riding kit, they insisted we have a go. We had to borrow leathers and helmets, but they came from Japanese riders who were smaller than us. I was very uncomfortable, but went through the motions. We said we liked it and that we could sell it.”

But if the GT750 was well established as a gentlemanly high-speed tourer when the first bikes reached dealers in the UK, the faint hope that it could be a fire-breathing monster was fuelled by the news that the factory in Japan had been working on a racing version. With the objective of winning the following year’s Daytona 200 race, and the US national series, Suzuki had produced bikes with special engines churning out 107bhp at 8000rpm, a phenomenal figure at the time. In practice for the race, the TR750s were the fastest ever fielded, topping 170mph on the Florida bowl.

Simply sophisticated

Once the GT750 had arrived, more about its technicalities was revealed. The crankshaft was like previous Suzukis, being pressed-up with four large roller bearings, but at 120-degree intervals, and with the primary drive by helical gear between the middle and right-hand pots.

Overlapping the transfer ports reduced the overall width to 71cm. Like the T500 Cobra twin, bore and stroke were 70 x 64mm, giving a capacity of 738.9cc. From exhaust-port closure the compression ratio was a modest 6.7 to 1. Steel liners with simple porting – an oval exhaust, two transfers and an inlet were cast into the aluminium-alloy block which was topped by a cylinder head casting secured with 11 studs.

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