The genesis of the TZ750

Lagging behind the competition in the early 70s, Yamaha needed to come up with something seriously special to stand out. So that’s exactly what it did...

We’re chronologically jumping around once again in this anthology of two stroke race machinery. We’re back with the tuning fork brand to briefly review one of the most awe-inspiring, successful and arguably fearsome pieces of kit to ever turn a wheel – the legendary TZ750.

On the early 1970s showroom floors where sales generated the money to go racing Yamaha was losing out in terms of big bike sales. The XS650 twin was its largest capacity machine but it was a twin cylinder four stroke and had something of a staid, sensible image. Suzuki had the glorious liquid cooled GT750 triple, Kawasaki had the brain-out, tarmac-searing H1 500, Honda was still well with the CB750, and Triumph of England had finally sorted out the worst of the Trident’s styling issues. Yamaha had nothing to compare and the management knew it. Ever up for a challenge, the firm’s designers delivered the jaw-dropping GL750. With four water-cooled, two stroke cylinders, fuel injection and reed valves, the new Yamaha superbike stopped the punters in their tracks at shows in Japan and Europe. Yamaha only gave away a horsepower figure – 70+ at 7000rpm and little else – but it didn’t stop the public from clamouring for details such as price and availability.

The official line thrown out by the factory at the time was that the GL750 was just a little way short of being production ready. Production was only waiting for management to green light the project and it would be on sale shortly. That the bike never made it to the showrooms is a well established fact. However, the back story perpetuated by certain importers is that, at least in the case of the machine sent to Europe, was a mix of genuine components allied with carefully finished wooden cases and handmade panels. The inference is that the GL750 was just so much spin and was never truly ever destined for series production. The GL750 was nothing more than a carefully construed mock-up.

Truth or fact, lies or myths? It’s unlikely that Yamaha will ever tell, but it is a well-known fact that at least one, if not two of these machines with their unique off-white seats, have been occasionally spotted deep within Yamaha’s museum complex. What we do know from contemporary sources and subsequent examination of commercialised Yamahas of the period is that the 750 was a lot closer to being production ready than many want to acknowledge. The bike borrowed heavily from the TX500 and TX750 four stroke twins that Yamaha saw as the future. The GL’s tank and seat base were 500 in origin, along with the European market’s twin front discs and brake calipers. Gauges, dashboard and controls were borrowed from the then flagship 750. The flanged alloy wheel rims made by Takasago were also TX750 derived and would soon also be used on the firm’s XS650. Yet, surely those four fuel injectors were simply mock-ups? Apparently not… they were taken from Yamaha’s latest snowmobiles and had been used in anger. Perhaps the greatest giveaway is the frame of the ill-fated TX750 twin. Getting up close and personal with one, it’s readily apparent that the chassis is substantially stronger in key areas than it needs to be. Why would the factory go to the extraordinary lengths to double skin and gussetting the steering head of a 750 twin offering a lowly 63bhp? The TX’s chassis was supposed to be shared with the GL!

Yamaha almost certainly pulled the plug on the GL750 in anticipation of impending USA emissions regulations on pollution, but if that is the case why invest so much money in a new flagship model? The 1973 Tokyo Motorcycle Show revealed the answer. Yamaha was going Formula 750 racing with the TZ700, aka TZ750, which

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used the GL750’s engine cases! Had Yamaha totally blindsided the racing opposition all along by suggesting the GL was a road bike, yet they’d been secretly developing the mighty TZ all along?

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