Different Strokes

While it might be true that Yamaha killed 750cc production racing with the slightly terrifying TZ750, this is proof they did intend it to be related to something in the showroom. The GL750 was part of the shock and awe Tokyo Salon 1971 show, and at the Paris Salon the following autumn it created a sensation on the Sonauto Yamaha stand. This would be the only time that the GL750 would leave Japanese soil, although there were rumours that as many as 800 were delivered to France. But that seems unbelievable – surely at least one would have resurfaced by now? Anyway, there are hints of other models in there: the TX750 four-stroke twin’s dashboard and frame, and the bottom crankcases of the YZ648 TZ700 prototype.

The fuel injection was apparently induction pressure driven – note the lack of cables – a bit like modern chainsaws. Yet those who saw it tested in Japan confirmed it ran Mikuni carburettors, as did the RD250 that debuted alongside it in Paris late in 1972. Meanwhile the world was on the brink of a fuel crisis that led to shooting in queues for gas in the US. Ralf Nader was also changing California’s approach especially to dealing with the perceived impact of motor vehicles on people’s lives. 1971 had brought the Environmental Protection Agency, and at the same time the success of the `69 Honda CB750 and Kawasaki Z1 were grabbing the headlines. Two-strokes were a no go.

Looking back 50 years later the H2 Mach IV Kawasaki triple might be an exotic collectible, but in 1972 it was a crude old thing compared to the sophisticated and smooth four-stroke fours, and after 1975, the H2 was history. No doubt the liquid-cooled Yamaha would’ve been smoother and more powerful than the H2, but the writing was on the wall for the strokers. Despite a brief fumble with a prototype rotary powered motorcycle after years of nothing but two-stroke motorcycles (bar the 650 twin) Yamaha embraced four-strokes with the XS750 triple, the XT500 and XS1100 four. Poppet valves proved to be the future.

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