Z1 The original ‘real’ superbike is still a convincing statement of power, performance and style
THE MACHINE THAT cemented Kawasaki’s reputation as the ‘horsepower factory’ was unveiled at the Cologne bike show in 1972. Yes, that’s 46 years ago, and still this motorcycle’s reputation as the first proper, OMG superbike remains undimmed.
Beaten to the punch by Honda launching the CB750 at the Tokyo show in 1968 when Kawasaki were already in the late stages of developing their own 750cc four, Heavy Industries shelved their effort. Hard to imagine how infuriating that must have been. Undeterred, they waited, worked, tested, waited some more, tested some more, and then – sure they had a product superior in every way – dropped the 903cc Zed into the public domain to huge effect.
With their wild H1 500 triple and H2 750 two-strokes already on the market, Kawasaki was almost a byword for unfettered lunacy. The Z1 would be different. Fast, yes, 12 second standing start quarter miles and a 150.8mph top whack (at Daytona International Raceway), and yet civilised too.
The design and build team, headed by Gyoichi ‘Ben’ Inamura had it in their heads to produce, as they put it, ‘one piece of motorcycle’, meaning they knew how to do power (H1 and 2 as exhibits A and B), yet aimed to make the Z1 a complete package that actually handled acceptably well for the time and made silky but substantial power off the bottom, through the midrange and at the top-end too. And it had to look like nothing else.
They absolutely nailed it on all counts. But hey, something that still looks this good today can be excused handling that has not improved with time – the H1 and 2 weren’t exactly wonderful in the chassis department either, but most people today are quite prepared to overlook this minor deficiency.
So terrified of the Zed being perceived as in any way underengineered, Kawasaki made the engine as tough as an anvil. Their two-stroke experience led them toward a nine-piece, pressed-up roller bearing crank that defied destruction. Straight cut primaries fed drive into a substantial five-speed ’box and the double overhead cam system with (best practice for the time – and still today) bucket and shim valve actuation. In ’72 this was almost space age.
They were also commendably obsessed with making this complex device as easy as possible to maintain; cylinder head and block are removable with engine in situ. The Zed engine is still a paragon of dependability and one of the most handsome air-cooled powerplants ever produced (especially in the original black).
The essential engine architecture lasted until 2000 when the Zephyr 1100, born of the GPZ1100, itself a child of the original Z1, finally shuffled away. That’s a 28-year stint. Not bad going. The 903cc engine became a 1015cc unit for the Z1000 in 1977 with the bore taken out from 66 to 70mm (the original bore and stroke dimensions were square at 66 x 66mm). This guide deals only with the 903cc machines: the 1973 Z1, the 1974 Z1A, 1975 Z1B and the 1976 Z900 – the earlier and purest versions.
Unsurprisingly these are the most sought after (and consequently the most expensive) of the big Zeds with the better original examples changing hands for up to £17,000, tattier machines for around £10,000. Tampered with, barely original bikes are still fetching thousands, and even rotting basket jobs are now more than just a couple of grand. If nothing else prices speak volumes about just what a benchmark superbike the Z1 was. The only consolation if you lust after a Zed, but fall short in the cash department, is this: they’re a lot better to look at than to ride.
Both looks and engineering have stood the test of time