1973 Kawasaki Z1: King of the Road

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Honda's legendary four-cylinder CB750 may have started the fire, but when Kawasaki's twin-cam Z1 came on the scene the Japanese Superbike wars heated up fast.
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Side panels made sure everyone knew the Z1 had the goods.
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Honda's CB750 may have started the fire, but when Kawasaki's twincam Z1 came on the scene the Japanese Superbike wars heated up fast.
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Kawasaki Z1
Years produced:
Total production: 85,000 (est.)
Claimed power: 82hp @ 8,500rpm (factory)
Top speed: 120mph (period test)
Engine type: 903cc air-cooled, in-line four-cylinder
Weight (wet): 246kg (542lb)
Price Then: $1,895
Price Now: $1,700 to $8,500
MPG: 43 (average)

Troyce Walls is generally a nice guy, but he’s always getting into trouble with British motorcycle enthusiasts.

Arguments start when he compares the handling of his 1973 Kawasaki Z1 to that of a Norton Commando. “The Z1 handles as good as a Norton. I’ve been arguing about the Z1’s handling with Norton people for years,” Troyce says. He also tees off Honda Four fanatics when he says, “The Z1 also handles much better than a 750 Honda of the same period.”

But Troyce figures he has the right to his opinions. After all, he has owned, worked on or ridden most of the better known motorcycles of the last 30 years — including Nortons, Hondas and Kawasaki Z1s.

Troyce grew up around mopeds and scooters — one of his early scoots was a leaky Cushman Eagle. “It used a quart of oil every eight to 10 miles, but the wind was in my hair, even if the oil was on my leg,” he remembers. The motorcycle bug bit, and Troyce spent his summers working at a local Honda shop. Soon enough he found himself in college, and after graduating Troyce spent several years in serious party mode, a motorcycle always at hand.

In the mid-1970s, Troyce was running around on a clapped-out Norton. “My ex-roommate called from Birmingham, and said he was going to ride his new Kawasaki Z1 to California. Naturally, I jumped on the idea and quit my job. I was supposed to meet him halfway between where he lived and where I was staying, about 100 miles — I had to spend six hours working on the Norton before it would even go that far. I finally met up with him and he let me ride his bike. I was impressed beyond words.”

This part of the story alone is enough to get most Norton fans chewing the wallpaper, but it gets worse. “The next morning, the Norton broke down again. My friend refused to ride with me if I was going to ride the Norton, so I went to the local Kawasaki dealer and traded the Norton for a used Z1. But a few months later, I was out of cash and had to sell the Kawasaki. I delivered the bike to the new owner, and I swear as I was leaving, the handlebars turned towards me.”

Z1 Origins
The Z1 was the successful result of an intense effort by Kawasaki to make a major splash in the motorcycle world. Kawasaki Heavy Industries is an old Japanese company, and was one of the first to start large-scale manufacturing when Japan began rapid modernization in the late 1800s. The Kawasaki Dockyard began building ships in Tokyo in 1878, but soon branched out into locomotive and bridge building, and, in 1937, aircraft manufacturing.

Small motorcycles became a popular means of transportation in Japan when imported motorcycles began coming into the country in the 1920s. Soon afterwards, fledgling manufacturers started building Japanese versions of these imported bikes. One of these was Rikuo, who built copies of Harley-Davidsons under license: Troyce owns one of the few Rikuos in the United States. Another was Meguro, who started making copies of four-stroke British motorcycles in 1937.

By this time the war Japan would lose was breaking out in Asia. By the end of hostilities in 1945, Kawasaki found itself out of the aircraft business. Still in possession of a large, well-equipped machine shop, the company turned to building motorcycle parts, and eventually complete motorcycles: Kawasaki’s first bike, the 1954 148cc KE of 1954, was built at the aircraft factory.

Japan’s economic recovery was slow, but by the mid-1960s motorcycle sales, which had dropped in the late 1950s, had taken off again. It was, however, a very different market. In the 1940s, the public needed cheap transportation. In the new markets of the 1960s, young and newly affluent people, especially in the United States, were interested in the sport of motorcycling, and demanded big, fast machines.

The Japanese were quick to respond to the market, and by the late 1960s Japanese motorcycle manufacturers were displacing the British companies that had dominated the global motorcycle market for years. There were many reasons for this, including support from Japanese banks and the government for industrial innovation. But a critical element was the willingness of the Japanese manufacturers to forgo immediate profit in favor of long-term investment.

While the British factories were still using prewar equipment to build motorcycles, Honda, Suzuki, Yamaha and Kawasaki purchased new tooling to produce up-to-date designs to tight specifications. In the late 1960s and early 1970s, Japanese bikes may not have had the excellent handling characteristics of the Italian and English bikes, but they did have electric starters, leak-proof crankcases and bright headlights.

In contrast, the British factories, whose owners would not — or could not — invest in new manufacturing equipment, continued to produce motorcycles that weren’t far removed from the late 1940s. Enthusiasts loved the British designs, but the average rider wanted to hit a starter button and go. And on Japanese bikes, they could.  

Against this backdrop, Kawasaki decided to attract attention by designing a two-wheeled rocket ship: The Mach III, a three-cylinder, two-stroke powerhouse, was unveiled in 1968.

The Mach III (also known as the H1) produced a claimed 60hp from its piston-port two-stroke engine and was good for 125mph. Although it had exceptional straight-line performance, the Mach III’s uncertain handling and inadequate brakes (for the first couple of years at least) made it into something people either loved or hated. Either way, the Mach III got Kawasaki what it wanted: instant name recognition and a reputation for making very aggressive motorcycles.

About the same time that the Mach III hit the market, Kawasaki’s engineers started working on a big four-stroke. There were several reasons for concentrating on four-stroke development. For starters, Kawasaki was acutely aware of a building sentiment to tighten environmental regulations, and that it would be difficult to build two-stroke engines to meet strict emissions standards.

And surveys and dealer interviews established a customer preference for a large-capacity four-stroke: And retailers felt a four-stroke would have broader appeal to the motorcycle buying public than the drag strip-inspired two-strokes Kawasaki was building.

Kawasaki’s large displacement four-stroke project, code-named “New York Steak,” was well underway when Honda presented its 750 Four at the Tokyo Motor Show in October 1968. Kawasaki was shocked by Honda’s new 750, and decided the New York Steak had to be bigger and better than the 750 in every way. Kawasaki abandoned plans for a release date in the near future and went back to the drawing board.

The Steak was originally intended to be a 750, but grew considerably before it was finally unveiled in late 1972. The new Kawasaki engine featured four compact cylinders and was only a half-inch wider than the contemporary Honda Four. It had an exactly square bore and stroke (66mm x 66mm) for a displacement of 903cc and double overhead cams. Eighty-two horses were claimed to be on tap  (although magazine tests showed this to be somewhat optimistic), and the big bike’s estimated top speed was 133mph (period tests gave 120mph).

Despite producing what was at the time amazing power, the Z1 ran on regular gas, featured emissions-control piping and ran a compression ratio of 8.5:1. It was marketed as a Grand Prix tourer: a fast bike with excellent handling and reliability.

Upon its release, the Z1 was the front-burner test project for all of the motorcycle magazines, and testers raved about the smoothness of the bike, with vibration damped by rubber mountings for the footpegs, headlight, speedometer and mufflers. Starting (either kick or electric) was easy, acceleration was linear with no flat spots, and straight-line stability was impressive.
Testers also noted the bike’s wide powerband, good low-speed manners, accurate steering and excellent handling on both tight mountain roads and big sweepers. Complaints centered on the rear shocks, chain and rear tire: all wore out way too fast.

In December 1972, Cook Neilson, Jess Thomas and Dale Boller conducted a Superbike comparison test for Cycle Magazine, pitting the Z1 against Kawasaki’s 750cc two-stroke, a Norton Commando, a Ducati, a Triumph Triple, a Honda and a Harley Sportster. The Z1 tied for the fastest lap times, came in second in the braking test (just ahead of the Norton) and turned a 12.386 quarter mile. It was one of the quietest in the test group, averaging 84.3 decibels. Cycle Magazine’s dyno rated the Z1 at 64.15hp @ 8,440rpm, 15 horses more than the Norton, which, although it was powered by an engine originally designed in the late 1940s, had a racetrack lap time only a second slower.

Kawasaki hit a home run with the Z1, and continued building bikes derived from its architecture for almost a decade. While hardcore Kawasaki fans will tell you the model died in 1975 when it became the Z900, visually little changed for the next two years. The real shift came in 1977 when the 1,015cc Z1000 was introduced, the model that signaled the end of the original King of the Road. Various iterations were produced over the next few years, including a touring version with shaft drive, and in 1981 Kawasaki turned out a Z cafe racer, which returned the bike to its roots after several years of increasingly sedate specification. The big air-cooled engine was finally retired in 1984 in favor of liquid cooling and four-valves-per-cylinder.

Back to the future
By the time Kawasaki stopped making Z1s, Troyce had cut back on the youthful pursuits of partying and traveling to the Coast on a moment’s notice, instead settling down to steady work. He kept riding, however, and began building a collection of bikes. And despite his experience with the Norton, Troyce has owned several British motorcycles, and a 1964 BSA A65 Rocket currently sits in his garage.

One of the bikes Troyce kept an eye out for was another 1973 Z1 — the bike that had turned towards him as he was leaving it that fateful day long ago. He started by buying pieces of the exhaust system. “I have had several ’75s, and a ’76 K1000, but I was looking for another ’73. Finally, I found this one in Fort Lauderdale in good condition. It had the wrong handlebars, a king/queen seat and the wrong exhaust, but it was otherwise okay and ran fine. The guy didn’t know what he had.” Troyce located the correct components and set the bike straight.

 “I’ve always had a special attraction to this bike. I still enjoy the way it feels pulling from low rpm up to where the afterburner kicks in. It’s a big bike, but I’m 6’2″ and it fits me,” Troyce says. “It has a few faults. Vibration may not have seemed so bad in 1973, but it blurs the mirrors at cruising speed, and the seat is hard for an extended trip.

“And it’s hard to get to the valve adjustors. The valves adjust with shims that sit in a depression on top of the valves. Kawasaki decided to use the shims to get precise valve clearances — at the time, it was an innovation. But you need special tools to adjust the valves, and if you race the bike and miss a shift, the bike may spit the valve shims out of the valve cover,” Troyce says.
You might say beauty is in the mind of the beholder. The Kawasaki Z1 has to be appreciated on its own terms — not as better or worse than the contemporary Norton Commando or Honda Four, but as an innovative motorcycle, a step ahead of the competition in many ways, but still very much of its time and place. As Troyce says: “The bike gives me a heavy dose of nostalgia. The color is perfect — hey, the overall visual is perfect. It does it for me: I like to sit on a stool and stare at the bike.” MC

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