Motorcycle History: The Kawasaki Two-Stroke Triples – The Dirty Dozen


(first posted 7/22/2012)   Around 1969, Kawasaki started developing a reputation for bikes that would pull up alongside you and then quickly leave you in a cloud of blue smoke. The fact that they sounded like a herd of chainsaws while doing so did not diminish this well-deserved reputation–nor did it matter what you were riding or driving, since they came sized for any competition.

Kawasaki did not come by its reputation by accident. Their constant goal was to build world’s fastest-accelerating production motorcycle; when the competition started catching up, Kawasaki would then build a bigger one. They eventually produced a family of four, ranging from 250cc to 750cc. Let’s take a ride on the wild side.


Sometime during the 1960s, Kawasaki realized they could make more money with large-capacity motorcycles. While they didn’t cost significantly more to build than smaller models, they did carry a much larger price tag. Their first effort was the W1. It essentially was a 650 copy of the BSA-A10, and it didn’t sell well. Perhaps since it was a first effort,  potential buyers simply decided to purchase the real thing (unlike today, there were quite a few new and competitive BSAs on the market).



Kawasaki had already started making a name  for itself as a producer of small-capacity, two-stroke twins when they decided to up the ante by building a world-beater 500cc twin. Using the very competitive 350cc A7 (above) as a starting point, Kawasaki began work on both a 500cc two-stroke twin and a three-cylinder design.



Supposedly, the big problem with making a triple was dealing with middle-cylinder overheating. The A7 depended on a rotary disc, but the difficulty in feeding the center cylinder demanded that Kawasaki go with a standard  piston-port, two-stroke design. Instead of feeding behind the crank, its carburetors attached to the bottom of the cylinder. (Ultimately, Kawasaki determined that the center cylinder never did present any sort of cooling issue.)

Another problem, spark plug fouling, was solved by boosting the voltage of the Capacitor Discharge Ignition to zap the plugs with 25,000-30,000 volts.


Judging by the A7, the 500cc rotary-valve twin could have been a world beater. However, Kawasaki was developing the twin and the triple side-by-side and the Suzuki T500 was a big reason they went with the triple: After all, why compete when you can build something new and totally your own? It must be noted that Honda’s CB750 was released very shortly after Kawasaki’s first try at a four-stroke DOHC 750; at the time, Japan was a hotbed of motorcycle development and Suzuki and Honda released first. Sometimes you have to wonder how different things might have been had Kawasaki beaten them to the punch.



In June 1967, Kawasaki announced the quickest production bike in existence, at least in terms of acceleration: The 500cc Kawasaki Mach I. Selling for $995, it was aimed directly at the T500. However, speed had better be what you were after, because the bike didn’t offer much over its competition.

Kawasaki had to be pretty happy with their pilot model. We were told that they’d set out to build the fastest-accelerating bike in the world, and in just about everyone’s opinion they had. In September 1968, the production bike was ready to be revealed to the world. Kawasaki had already made it available to the motorcycle press, whose reviews invariably praised the lightning-quick acceleration.

The bike was an air-cooled, two-troke triple of 498cc. At 7500 rpm it made 60 hp (you can compare the models in the chart below), but not the kind of power band we’re used to today.  Power turned on suddenly at about 6000 rpm. When you reached the rated 7500, you had only about 500 rpm left before there was an abrupt shut-off. Peaky bastard.

With fuel economy in the twenties, the 3.3 gallon tank didn’t take you far; still, only 383 lbs of dry weight meant you could reach the next gas stop very quickly.


A standard H1 would turn a quarter-mile in 12.4 seconds, at maybe 100 mph, but straight-line performance was its true strong suit.  While the H1 was never praised for good handling, it soon became known as the fastest thing on the road, provided the rider could hold on. There actually were some supermen who road-raced this bike successfully.


In the European Championships, Ginger Malloy took second place behind Giacomo Agostini.

I discovered a most entertaining story about a road racer learning to deal with the big Kaw. It involves a South African (now Aussie) named Kork Ballington and can be found here:

The transmission’s neutral position sat below first gear and the bike handled like it was hinged in the middle. It acquired plenty of names not assigned by the Kawasaki factory; some of the more popular were Widowmaker, Flexiflyer, Kamikaze 500 and Grenade Launcher.



A friend had one of these while I was stationed at Ft. Bliss. We met at the drag races one day, would spend time in the pits with him and his bike. The highlight was when when he ran against an MGB with a small block Chevy–and won. I’ll not forget the look on his face when I asked him if he might go faster with a hotter cam. Well, we live and learn. Or learn and live.

The Kawasaki had tremendous acceleration.  It was, literally, a moving target, and other bikes began to catch up. The reason the story doesn’t stop there is because Kawasaki copied Honda by turning a successful bike into a product line.

Honda offered a range of bikes that were similar in appearance, but different in size and performance. At one point they were producing seven models, from the CB100 through the CB750. Kawasaki apparently decided to emulate Honda’s approach; considering how little it took to differentiate the Hondas, I think Kawasaki did just fine.

Without a rider or other visual reference point, it takes a highly trained eye to differentiate these five Kawasaki models. Actually, the S1, S2 and S3 are the same frame size with different displacements.


Model Size 1st yr. Last yr HP Wt (dry)
S1 250cc 1972 1975 32@8500rpm 328 lbs
S2 350cc 1972 1973 45@8,000rpm 328lbs
S3 400cc 1974 1976 42HP@7,000rpm 328lbs
H1 500cc 1969 1976 60hp@7,500rpm 380lbs
H2 750cc 1972 1975 74hp@6800rpm 422lbs


The H1’s task was establishing a reputation, and it performed it very well.  In 1972 Kawasaki released their full line of two-stroke triples. I have broken them down in the graph above to clarify their individual places in the lineup. Also, I tried to get the same view of each bike to show their great similarity–one so great that I almost loaded a mislabeled picture of the 750 into the 400 slot.



The S1 Kawasaki was created primarily to capture the notice of younger riders. According to Wikipedia, limiting its displacement to 250cc provided cost advantages regarding insurance, licensing and operator permits, especially in England.


Mostly, the 350cc S2 was sized to fit within a particular racing class in Europe (that of the A7 Avenger) that had become outdated.



You’d think that the whole idea behind the 400cc S3 would be more horsepower, but as the graph shows, it has less power than the S2. Actually, this bike was created to provide ample torque at lower rpm than the S2 and was intended for street use, much like the T500.



H1: This is the trendsetter, created to provide the most acceleration of any production bike in existence.  Kawasaki’s problem was that the competition rose to the occasion, which led them to build the 750cc H2. The H1 found itself limited to street duty and racing, where its 500cc provided a class advantage.

I cannot think of a bigger two-stroke motorcycle in modern times than the 750cc H2. This bike inherited most of the quirks of its H1 predecessor. It did not handle as well as several of its contemporaries, it was terrifying to ride and its gas mileage was worse than many cars of the day.


Yvon Duhamel, Gary Nixon, and Art Baumann raced these bikes. They had mixed results but won several AMA national events with the H2. Nixon and Duhamel are pictured above. What definitely wasn’t mixed was the reputation these bikes enjoyed on the streets and on the strip.

Straight out of the box, the H1 would post a 12-second ET. The H2 was even hotter. Duhamel is pictured above, exiting the pavement for the dirt at about 100 mph. Tony Nicosia was one who both dragged the bike and went to Bonneville. Personally speaking, when I think of these bikes I think of the good old days, even though I was terrified of them and do not long for their return. They did what they came to do, and now they are gone.

Still, there are a couple of madmen out there who not only long for the old days but want to improve on them.


A man from England, Allen Millyard, made this five-cylinder Kawasaki (S3 Barrels). Both this bike and his KZ1300 V12 are all over the web.  Google him.


But the big boy is this bike with 48 S1 cylinders. At around 4200cc, I cannot imagine how one would keep this thing in rear tires, or even hang on–but what I can imagine is the plethora of homemade bikes out there, some of which I encountered while chasing Syke’s clue for Millyard’s bike. Yes, it will take a while, but I do feel a story coming on.