When The 1969 Kawasaki H1 500cc Triple Was King

Kawasaki’s three-cylinder two-stroke took the early 1970s by storm.

Kawasaki H1
This factory-fresh example of an H1 was photographed by Kawasaki a few years ago and described as “perfect.”Kawasaki archives

In 1977 I knew when it was last call in the bars two miles away, for I could hear that musical three-cylinder sound of Kawasaki H1s and H2s upshifting away into the night. Today, four decades later, the sound has defaulted to Harley-Davidson Sportsters. At the end of the 1960s if we were working late in our Boston-area shop, customers would come in to describe with excited hand gestures their evenings of hunting down and smoking off Sportsters and Triumph Bonnevilles. Waiting for them, outside the local bar, The Ebb Tide. The old kings were fragile, and easily felled. Kawis ruled!

Our East Coast Kawasaki service manager, Eddie Moran, showed us how: Stand over the running bike; bring up the revs; drop the clutch; and with back tire spinning, sit down and leave it all behind.

Kawasaki’s so-called N100 plan—to take over the U.S. high-performance motorcycle scene—was hatched in 1966–67. It began with an estimate of the required performance. After considering Sportster, Bonneville, BSA Super Rocket, and even Honda’s middle-of-the-road CB450 twin, the basic spec was pegged at 500cc displacement, 60 hp and a 13-second quarter-mile time.

The British bike industry faced the same problem, but was paralyzed by its end-of-days business model: “Fix the problem. Don’t change anything. Don’t spend any money.”

"The old kings were fragile, and easily felled, Kawis ruled!'

Kawasaki engineers knew that their W-Series four-stroke twins, based on BSA’s A-7, couldn’t make the numbers.

The answer was the lightness and torque of two-strokes. Now the decision fell between enlarging the already-once-enlarged A7 Avenger’s 350 disc-valve twin, or taking a new direction. I suspect that 500cc A7-based twins were built and tested, with the usual result that the bigger the piston, the more vulnerable it was to seizure. And the A1 Samurai and A7 Avenger lines weren’t cheap to make, with all the extra seals, covers, and gaskets required to implement its high-performance disc-valve intake system.

1969 Mach III 500cc H1 Triple
As the 1970s were about to begin, emissions legislation was taming the great muscle cars—but motorcycles were just getting started. Kawasaki lit the fuse with this 1969 Mach III 500cc H1 Triple.Kawasaki archives

Smaller pistons meant more cylinders. Cost control meant no more disc valves—the new engine would have piston-port intake. Somehow the engineers’ choice leaked to the English magazines and was airmailed to our little dealership: three cylinders. Would they take the narrow form adopted by DKW in the 1950s, the center cylinder horizontal, with the outer pair upright? Or would it be three straight across?

Kawasaki chose three-in-a-row, but not before submitting the layout to specialists at Osaka University for cooling studies. One source almost certainly consulted was Julius Mackerle’s “Air Cooled Motor Engines,” still so much in demand today that it typically goes for more than $100. (It’s great for things such as optimum contours and spacing for cooling fins.) Another likely source was the special methods used by engineer Luke Hobbs to achieve equal cooling of the 28 cylinders on Pratt & Whitney’s giant R-4360 piston engine. Remember—Kawasaki was originally an aircraft manufacturer.

One clear result of the Osaka University cooling work is the H1’s wide cylinder spacing, at 115 mm almost 20 percent greater than in contemporary twins. The fins of the center barrel and head were made longer fore-and-aft, than those on the outer pair—with adequate room between for throughput of cooling air. It was, in the words of Yvon Duhamel’s roadrace tuner Steve Whitelock, “A nice little engine. Really good.”

1969 Mach III 500cc H1 Triple
Yes, there were problems: drum brakes, skinny tires and fork tubes, shocks that looked better than they worked. But they were rocket ships that the miracle of mass production could make yours for less than a grand.Cycle World archives

It worked, and despite being more than 20 inches wide, the triple easily hit the N100 numbers. A chronic problem for dealers would be the ambitious capacitor-discharge ignition, firing special surface-gap BUHX sparkplugs. Use of a distributor brought the usual problems of corona—an under-cap “plasma glow” of electric energy bleeding between cylinder wire contacts that often bloomed into actual arcing—and a blizzard of warranty fixes. As delivered, oil-injection metering pumps were set to maximum, making big smoke from the tailpipes. Much less oil worked perfectly well once break-in was completed.

Handling was widely criticized, and I can offer two clues. One was my visit to the H1 chassis line in 1972, where I saw one side of the steel frame completed, then flipped it over and saw the other side welded in place. Normally, welds are made on alternating sides, to zero out heat distortion. Another was that when I disassembled a rear damper, I found that its top O-ring had, during assembly, flipped to assume a D-shape. That damper pumped out all its oil in a few strokes. But in those days suspension was as mysterious as existence, so almost nobody removed the springs to check for equal damping.

Cliff Carr
Do I see a cautionary finger on the clutch? This is the late Cliff Carr on my 1972 home-built Kawasaki 750 triple. Disc brakes, C&J tank, 41mm fork tubes, Koni shocks. I can almost hear it.Cycle World archives

The bikes were fast—a revolution. The Kawasaki H1 put a stop to any thought that pushrod four-strokes could compete by being bored out and revved-up even more. Forget it. So in that sense, the H1—and the 50 percent bigger H2 of 1972—forced four-stroke designers to build really big engines, such as Kawasaki’s 903cc Z1 of 1973, with serious DOHC cylinder heads. That, plus the U.S. Environmental Protection Agency mandate for cleaner air, was the only way to put the grinning two-stroke genie back into its bottle. Yet 110,000 H1s were built.