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Kawasaki Square Four 2 Stroke Prototype

A LOOK BACK IN HISTORY.

Some thirty years ago, the Japanese economy experienced a period of particularly high economic growth from the mid-1950s until the mid-1960s. Kawasaki grabbed this opportunity with both hands and the company’s production of motorbikes surged in response. Then some time around the middle the 1960s marked the start of the Supersports era.

Kawasaki rode the wave generated by what later came to be called the Izanagi Boom and, in September 1966, the company proudly announced its W1, a motorcycle with a displacement of 650cc — at the time of its launch, this was the largest displacement bike on the Japanese market. In August 1967, the A1, more commonly known as the Samurai, took center stage — this was a high performance machine with approximately 80ps per liter. It was quickly followed by a larger bore model, the A7.

This was undoubtedly the era when Kawasaki laid the foundations for its current success.

Kawasaki, however, was not the only manufacturer that had the presence to take advantage of those economic boom years. Honda launched its CB450 during the same time and Suzuki its T500. Both these models proved to be very popular with enthusiasts overseas.

At the time, the motorcycle riding public keenly sought larger bore machines with higher horsepower and higher top speeds and each company vied to provide what the market wanted. In the US — America was the world’s biggest motorbike market — riders were particularly insistent on these new features. Unfortunately, when these demands reached the desks of the manufacturers back in Japan, they usually were accompanied by calls for lower prices.

Obviously this was not going to be easy for the Japanese bike manufacturers.

Kawasaki’s response was to put together a top secret plan referred to as the N100 Plan. Development got under way in earnest in July 1967 with the eventual target becoming a set of specifications that were nothing short of spectacular for the period: an engine capacity of 500cc, 60ps output (equivalent to a per liter horsepower of 120ps) and a 0-400m standing start time of 13 seconds.

Kawasaki considered two different approaches to the construction of what would become the most powerful production motorcycle engine for its day. The first approach was the tried and trued route of increasing the bore of an existing engine — this would, at least, assure the company of the increased power output they were after.

For this application, Kawasaki looked at increasing the bore of the successful A7 to obtain an air-cooled two-stroke parallel Twin cylinder rotary-disc valve engine with a displacement of 500cc. The second approach involved the development of a revolutionary new engine layout, which went completely against the conventional wisdom of the day. In creating the fastest bike in the world, the engineers would have to rewrite all the technical manuals, building either a parallel or L design air cooled two-stroke three cylinder engine.

In any event, both twin cylinder and three cylinder engines were developed alongside each other. The most crucial problem in the development of the three cylinder model was to decide whether to go for a parallel in-line layout or develop a new L cylinder layout. With this in mind, Kawasaki began by experimenting with the most troubling aspect of the three cylinder engine: How best to cool the second or middle cylinder.

In order to test the cooling potential of both engine layouts, the company’s technical team prepared a mock-up of each engine which they then took to the laboratories of the Faculty of Engineering at Osaka University. After conducting a battery of tests and collecting the data on the heating and cooling characteristics of the engine itself, the information was used to evaluate everything from the optimum length of the cooling fins to the optimum cylinder pitch. The results of these tests led to the conclusion that cooling efficiency would not be significantly impaired by arranging the cylinders in parallel and the company finally opted for the in-line cylinder layout.

At the same time that the three cylinder engine layout was under consideration, Kawasaki also pushed ahead with the development and testing of its two-stroke twin cylinder rotary disc valve engine. The preliminary test results pointed to a very promising outcome. However, once the layout of the three cylinder engine had been decided, the technical team applied themselves wholeheartedly to development of the two-stroke three cylinder piston valve engine that was ultimately to become legendary.

Their efforts culminated in the successful launch in June 1967 of the H1: a 60ps / 7,500rpm, 120ps per liter engine.

Two different engines were thus developed side by side but, in the final analysis, the company opted to go with the brand new feel and stunning design of the three cylinder piston valve engine.

The technical team’s most immediate problem for mass production of this monster engine was how to prevent the plugs from fouling at low speeds. The outstanding Kawasaki Integrated Powervalve System (KIPS) — the internal combustion management system that is common place today — was at that time yet to be invented and, in the absence of this kind of exhaust control device, it was difficult to obtain proper combustion at all engine speeds.

The Kawasaki technical team responded to this challenge by borrowing from existing 2-stroke racing technology.

Cutting edge CDI (Capacitor Discharge Ignition) technology from the latest KR-3 works racer (with a water cooled two cycle four cylinder V-type 125cc), was adopted for the H1. This ignition system worked by first boosting an initial 12V to about 400V. Next, it boosted the voltage to about 25,000 to 30,000V by means of a thyristor-based switching system. The powerful spark that resulted opened the way for a quantum leap in combustion efficiency.

The introduction of CDI also made it possible to utilize the high performance ignition capability of the surface gap spark plug which in turn reduced the amount of unburned fuel mixture in the cylinders.

In this way, with the help of the latest technology of the day and some of the techniques and know-how the company had built up in the development of famous models such as the A1, A7 and KR-3, the technical team was able to develop an engine which gave them almost everything they were hoping for in terms of speed.

At the same time, however, this was not the only challenge the technical team had to overcome. The massive horsepower developed by the new engine would clearly have to be borne by the frame — horsepower levels that proved to be too much for the existing A1 or A7 frames. The upper rail sections of todayUs double cradle frames normally consist of twin or triple top tubes.

At the time, however, single pipe backbone construction was the norm and 60ps was almost too much for it to take.

After much research, the frame design team finally came up with a solution which was to run twin frame rails from the steering head back to the seat rail and to reinforce them at three intermediate points. The suspension was another area in which exhaustive research had to be carried out. Taking their lead from the front fork pioneered in Italy by Ceriani, the team developed the first inner spring telescopic front fork to be incorporated into a large displacement Japanese motorbike.

At the same time, the team also opted for a rear suspension with a three-position spring preload adjustable shock absorber.

With unshakeable resolve and complete faith in their research, the technical team overcame one obstacle after another until finally they reached the point of test driving a prototype.

After their long struggle to reach the position of developing the fastest bike in the world, the technical team watched with satisfaction as their pilot model broke the 190 km/h barrier with ease. While they could be forgiven for thinking that victory was within their reach, it was only now that the problem which was to give the technical team their biggest challenge of all first appeared — running a bike continuously at speeds of 190 km/h plus mercilessly stripped the tread from the tires.

To develop a tire that would stand up to continuous ultra high speed running, the technical team got together with Dunlop to develop the revolutionary K77. This was much more akin to a racing tire than an ordinary street tire in that they abandoned the traditional rayon cord in favor of nylon cord. After development of this new tire, test runs were restarted and final development of the new bike proceeded on time.

With the development of the basic engine and chassis design specifications well under way, the company’s design team began turning its thoughts toward creating styling which would best suit what would soon be hailed as the world’s fastest motorbike.

The sculpted eguri gas tank design — one of the characteristic design features of the MACH III — was part of an overall design scheme worked out primarily in the US side except for the asymmetrical layout of the three exhaust pipes, contributed by the factory design team. Although the unusual layout for the exhaust flew directly in the face of the opinions of the American designers who were adamant that a symmetrical design would be best, it was eventually adopted for performance reasons.

Finally, approximately 14 months after the N100Us initial planning phase began in July 1967 and after applying every last ounce of its available technical know-how, Kawasaki produced the first ever MACH III in September 1968.

From the start of production into the early part of 1969, Kawasaki busied itself shipping samples of the new machine to every corner of the globe where it was universally welcomed with praise by all the best trade publications and commentators.

With the sleek, Luminous whiteness of its body, accented by dark blue stripes along its tank, shining asymmetrical triple mufflers, and powerful engine with maximum output of 60ps / 7,500rpm and maximum torque of 8.5kg-m / 7,000rpm. the MACH III captured everyone’s heart. Not only that ,but retailing at just US$995 at a time when the average stateside selling price for a 750cc machine was around US$1,400. the growth of the new machine’s popularity was nothing short of explosive and it became a best seller almost overnight.

The new Kawasaki in Peacock Gray with black stripes went on sale in the Japanese market in September 1969 under the name 500SS MACH III, again with a reasonable price tag of just 4298,000.

June 1970 saw the launch of a candy red bike with white stripes and a few minor changes. This was followed in September 1971 by the H1A, a variant model without the sculpted eguri gas tank. In January 1972, the company brought out the H1B with battery powered ignition, disc brakes at the front and a front fork like the H2. A steering damper was also added, and the machine debuted under the name Rainbow Color.

The H1D, which came out in 1973, had a seat cowl added like the H2, the CDI unit was changed to that of the H2, and the steering damper and rear brake air scoop were both dropped. Subsequently, the H1E, which was introduced with a new CDI, evolved into the H1F with a different color and graphics. Eventually, more than 110,000 units of this model left the factory for destinations all over the world.

It has been almost 30 years since Kawasaki first started to develop its MACH III 500SS, but, even after all this time the H1 is still much loved and prized by a great number of Kawasaki fans around the world.


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