KAWASAKI Z1 FASTEST, MEANEST FOUR
‘Was it really 43 years ago that Kawasaki launched the Z1, and overnight rewrote the book on two-wheeled performance so dramatically?’
AT AN INDICATED 160 km/h it’s a hell of a thrill. You’re crouched down in a vain attempt to escape from the wind, peering over the clocks and with arms raised to high and wide handlebars. The big engine is sucking audibly through its open-topped airbox beneath the seat, and howling louder through four chrome silencers as the mighty Z1 speeds along with the force and style that once made it the undisputed king.
Then you glance down at the steering head and realise that the bars don’t just feel light, but that they’re moving slightly yet visibly from side to side under the strain being fed into the chassis. It’s not quite a weave, but it’s not far from becoming one — and it shows the other side of the Kawasaki’s personality. The motor’s smoothness and easy speed could almost deceive you that this is a modern multi. But superbikes were very different when the Z1 ruled the roads.
Was it really 43 years ago that Kawasaki launched the Z1, and overnight rewrote the book on two-wheeled performance so dramatically? The first Zed retains a style and presence that make it seem far younger than it is. Few naked bikes of more recent years have come even close to matching the look — rounded and gentle, yet at the same time raw and brutally powerful — that helped make the Z1 such an instant success.
It was pure performance, though, stunning by 1973 standards, that announced the Z1’s arrival and ensured its lasting fame. This bike’s 220-km/h top speed was over 15 km/h higher than that of Honda’s CB750, until then Japan’s finest superbike; and the Kawasaki’s standing quarter-mile time of 12.5 seconds was more than a second quicker. Neither the Honda nor anything else could keep it in sight.
Yet the bike that established Kawasaki’s lasting reputation for power with reliability might never have been built. In the autumn of 1968, Kawasaki’s engineers had been dismayed when, with their own plans for a four-cylinder 750 well advanced, Honda had unveiled the CB750. Rather than abandon their project, code-named “New York Steak”, Kawasaki learned all they could from the opposition, enlarged their own engine to 903 cc, and returned four years later with the Z1.
Their efforts were rewarded, because the Z1 powerplant — with square dimensions of 66 x 66 mm, compression ratio of 8.5:1, and twin camshafts working eight valves via bucket-and-shim adjustment — was in a class of its own. Its claimed maximum output of 82 PS at 8,500 rpm meant the Kawasaki was fully 15 PS more powerful than the smaller, single-cam Honda.
The Z1 motor, with its distinctive round-ended cam-cover, was angled slightly forward in a chassis based around a conventional twincradle steel frame. Front forks held a 19- inch spoked wheel, with a single 295-mm disc brake. A second disc and calliper could be fitted
as an extra, using lugs already fitted to the right fork slider. Twin rear shocks, adjustable for preload, held an 18-inch wheel with a 203-mm diameter drum brake.
If the Z1’s chassis specification was ordinary, then its styling was inspired. Although understandably big and heavy, weighing 246 kg wet and with a 1,500-mm wheelbase (50 mm longer than the CB750’s), the Kawasaki looked anything but. Its slim fuel tank, small rounded side-panels, rear ducktail, four silencers and cleanly shaped front mudguard helped give an eager look that made the Honda seem dumpy and tame by comparison.
Those high handlebars and the Z1’s fairly forward-set foot-pegs were hardly designed to help exploit the bike’s all-conquering horsepower. But all these years on, the improbably relaxed riding position merely adds to the thrill of riding the Kawa, as you straddle the thick seat and look out over the simple dashboard layout of twin clocks with warning lights in the centre.
Immediately as the motor fires up, you’re reminded of one sensation lost to riders of modern motorcycles, because the Z1 burbles through its four pipes with a menacing sound far removed from the muted whine of today’s fours. The throttle and clutch are light, typically Japanese in their efficiency, and the Kawasaki pulls away feeling manageable thanks partly to a fairly low centre of gravity.
By today’s standards the four-cylinder engine’s tractability and docility at low revs are unremarkable, although more than four decades ago such sophisticated behaviour was impressive for a highperformance machine. Carburation of the four 28-mm Mikunis is crisp, the five-speed gearbox slick, and the big, torquey motor pulls happily from as low as 3,000 rpm in top gear.
There’s a little more vibration than from modern fours, enough to blur the mirrors much of the time, but the ride is acceptably smooth. The Z1 cruises at 130 km/h with just 5,000 rpm showing on the tacho, and with four grand still to come before the red-line. At that sort of speed the motor feels relaxed and unburstable — even if the exposed riding position means that description does not apply to the rider for long.
Thoughts of comfort are forgotten when at about 80 km/h in third gear you crack the throttle open to send the Kawa storming forward with an arm-wrenching surge of acceleration that is thrilling now and must have been mind-boggling back in 1973. These days the Z1 would barely outrun Kawasaki’s recently released Z650 twin, never mind the far more powerful modern Z900. But there’s a raw urgency about the old four-pot warrior’s power delivery that sends a tingle down your spine.
And the handling helps to make the ride exciting, because for all the Z1’s reputation as a fair handler in its day it is easy to see why the Kawasaki brought plenty of trade to chassis specialists such as Harris,
Martin and Bakker. Throughout my short ride, the immaculate, 1974-model Z1-A didn’t once misbehave seriously enough to become worrying. But at speeds above 130 km/h, the steering’s generally light feel did little to inspire confidence.
This machine has been restored to the condition it left the showroom in 1974, almost to the last nut and bolt. It is even correct in details such as its use of original type ball-race steering head bearings, instead of the superior taper-roller bearings commonly used as a replacement. After riding it, you understand why riders in the 1970s rarely left their bikes standard for long.
Fitment of a steering damper was a popular modification at the time, as was swapping the original shocks — which gave a comfortable ride, but rapidly lost damping control under hard use — for after-market units from firms such as Koni. Flatter handlebars improved aerodynamics and helped combat the Kawa’s vague feel at high velocities.
Handling at lower speeds was better, with stability helped by conservative steering geometry that meant the Z1 needed plenty of pressure on those wide handlebars for rapid changes of direction. Despite their lack of width by modern standards, this bike’s Metzeler tyres (3.50 x 19 inch ME11 front, 4.00 x 18 inch ME77 rear) gave enough grip to make grounding the Z1’s centre-stand easy.
Even the standard single front disc brake was fairly powerful, given a strong enough squeeze of the lever. That was just as well, because the twin-disc conversion was expensive, costing almost £100 (Rs 8,000 by current conversion rates) in the UK in 1973, when the complete bike sold for £1,088 (Rs 87,000). (More seriously, wetweather braking performance was appalling — with one disc or two.)
That purchase price was a lot of money in 1973, when the CB750 cost just £850 (Rs 68,000). (To put things in perspective, BMW’s glamorous R90S was far more expensive still, at £1,800, that is, Rs 1.44 lakh.) The Z1’s supreme speed made it an instant hit in Europe and, more importantly, in the huge US market.
Such was the Z1’s lead over the opposition that Kawasaki barely had to modify their flagship to keep it on top of the performance pile for several years to come. This machine, the Z1-A, differed from the original Z1 of 1973 in its paint scheme, alloy (instead of black) finish to the engine cylinders, and minor alterations to fork damping and carburettor jetting. The Z1-B of 1975 was cosmetically different again, and dispensed with the original models’ messy drive-chain oiler.
In 1976 the second front disc brake became standard fitment, while smaller carbs, reshaped combustion chambers and more restrictive pipes (all to reduce emission for the US market) reduced peak power from 82 to 81 PS. The bike also gained a new name, becoming the Z900. But one thing didn’t change. It was still the fastest, meanest four-cylinder superbike on the road.