If the CB750 was Japan’s first large capacity four, the Z1 was the world’s first superbike; raising the performance bar to unforeseen heights; leading a new era of big Japanese multis and setting the template not just for Kawasaki engines for the next decade, but for those of many other manufacturers, too. In virtually every way, the Kawasaki Z1 was The Daddy.
The mention of the Honda CB750 is deliberate. Simply: the Z1 would not have happened without it. Kawasaki had been developing its own 750/4, the N600, around the same time as the CB. When the Honda was unveiled, at the 1968 Tokyo Motorcycle Show, Kawasaki scrapped its version and vowed to respond with something even bigger, faster and more sophisticated.
Four years later, working under the project name New York Steak, the Z1 was unveiled at the Cologne Show in November 1972. It was a shock in every way.
First, you have to remember that until then Kawasaki was primarily a two-stroke manufacturer, known for lairy triples like the Mach 1 and small capacity trailies. Its only production four-stroke up to that point had been the BSA-alike 650cc W1. So why the change?
"Lots of reasons," Kawasaki General Manager T. Yamada said at the bike’s launch. "Kawasaki wanted to build the ‘King Motorcycle’, a bike beside which the finest motorcycles in the world would shrivel, a bike that would leave a hot and smoking scar across the face of the sport… and you just can’t do that with a two-stroke."
Second, the Z1 performed like nothing else. If its technology wasn’t new (there had already been bikes with transverse fours, twin cams and disc brakes), its slick combination into a huge package certainly was. The 903cc, 85bhp Z1 was 167cc bigger and 18bhp more powerful than the Honda, plus it had an attitude for thrills unlike anything before.
American road testers sampled it first – and were blown away. "The Z1 is the most modern motorcycle in the world. It is also the fastest. The first of a new generation of bikes capable of nattering down quiet country roads one minute and rotating the Earth with incomprehensible acceleration the next," said Cycle in November 1972. It subsequently went on to become MCN's Machine of the Year from 1973-76.
Immediately here was a new ultimate. If you could afford one, you owned the undisputed king of the streets. If you couldn’t, you wanted one.
And third, and just as importantly, is the Z1’s (and its successors) longevity. This was no fly-by-night; it reigned as performance king for most of the decade until finally deposed by Suzuki’s four-valve GSX1100E in 1980. By then Kawasaki’s performance king reputation was assured.
Even then it wasn’t all over. The Z1’s basic engine architecture lived on in the next-generation GPz1100 and it remained the basis of drag racers the world over. Even well into the 1990s, bikes like the Zephyr, Z750 and more owed their engineering to the Z1. Today, its stature as the father of all Japanese superbikes is beyond question. The word ‘legend’ is bandied about too often, but the Z1 is exactly that.
Today the Z1 is the most desirable of all Japanese classics. It has it all: it’s a performance landmark, is of technological significance, has racing heritage, is great looking, early models are scarce and it’s also still useable and enjoyable.
As a result, ultra-rare, original, first-year (1972) examples, as visually distinguished by the blackfinished cylinder block – just 30 were officially brought into the UK as there was no official importer at the time – now reach up to £20,000.
Luckily, if you’re less fussy, virtually identical later variants, such as the 1975 Z900 is far more numerous and can be had for as little as a third of that. What’s more, spares, advice and expertise are plentiful, a leading example being the UK’s own Dave Marsden – of www.z-power.co.uk – a world-renowned expert on the Z1 who has turned his love of the bike into a business buying, restoring, tuning and finding parts.
"The Z1 has become such an important bike primarily because of the era during which it appeared," says Marsden.
"The Honda CB750 was always a bit boring and the Z1 was the opposite.
"The fact it was a bit scary was all part of the image. The world was bored of unreliable British bikes. Kawasaki knew the two-stroke triples were unreliable so the fourstroke, four-cylinder Z1 was perfect."
