The "Z1", introduced in 1972, astonished the motorcycling world with its engine performance, handling stability, and durability. At the time, its performance capabilities were world -class, earning the Z1 and Kawasaki great respect. Since the later Z1R and Z1000J were developed along the same lines as the Z1, Kawasaki's air-cooled, 4-cylinder, 2-valve engine technology evolved even further and proved extremely popular among motorcyclists. At the same time, however; competitors were rapidly advancing their own technologies. Other manufacturers were undertaking new development efforts to build 4-valve single cylinder engines, V-shaped engines and rotary and turbo technologies, and on and on. Although Kawasaki maintained absolute confidence in its air-cooled, 4-cylinder, 2-valve engines, they had to admit that the appeal of the Z1's technology was beginning to pale. A decision was made, therefore; to develop a brand-new, high-performance, next generation motorcycle by applying everything Kawasaki engineers had learned through their Z1 experiences. This was in September, 1980.
One year passed before a prototype was produced. Amazingly, the engineers had mounted a DOHC air-cooled, 6-cylinder, 2-valve engine to it! Development goals for the new machine were high power output and low vibration and the 6-cylinder smoothly delivered more than 100PS with very little accompanying vibration. For a first-time prototype, its engine layout, impressively, was nearly perfect, but the Kawasaki Engineers were not satisfied. Why? Because the engine was too smooth and, they felt, somewhat tame, especially when their main objective was to develop a motorcycle that would shock the marketplace even than the "Z1" did.
So, they gave up the mild 6-cylinder and dared to build a DOHC, air-cooled, 4-cylinder, 4-valve engine. The decision to drop all of Kawasaki's previous 2-valve engine technology and embark upon development of a completely new 4-valve design, a first for Kawasaki, was based on the need for better charging efficiencies. And with the completely new design, Kawasaki could set motorcycle engineering precedent by adopting a secondary balancer to its new engine to control vibration. For a low center of gravity Kawasaki would, for the first time, adapt its diamond frame technology for a large-displacement, high performance motorcycle.
During the development of the GPZ900R, as with the developments of the MACH III and Z1, the engineers had to leap one technical hurdle after another. One challenge, in particular, was how to effectively deal with the extreme temperatures generated by high-performance, air-cooled engines. The high temperatures produced 'heat fatigue' that caused power output to decline and even warp the valve cover and other vital engine components. Kawasaki engineers quickly found that current air-cooled engine technology would not allow for the development of a durable, high-performance, 120PS air-cooled engine. After all, ten years had already past since the Z1 and its engine technology were introduced.
GPZ900R engine
"A liquid-cooled engine is the answer!" This statement completely changed the development challenges that laid ahead. Research and development efforts were carried out with new resolve and the original development goal of producing something better than the Z1 served to further to the engineers' fervour. Towards the end of 1982, exactly ten years after the introduction of the Z1, the first DOHC liquid-cooled, 4-cylinder, 4-valve prototype was produced. Wet liners were used for improved cylinder cooling efficiency, and the previous center cam-chain was moved to the left side to make the engine more compact. Although the production engine had a single cam-chain driving two camshafts, the prototype was equipped with two cam-chains; one from the left side of the crankshaft to the exhaust side and the other from the right-hand side of the exhaust to the intake camshaft, in an effort to make the cam sprocket as small as possible. By adopting the side cam-chain system, together with the new generator located at the rear of the cylinder, the engineers were able to realize a long-cherished dream of building small engines.
Next came the frame. It was Kawasaki's first attempt to apply diamond frame design technology to a large-displacement, high-performance machine. Because of the diamond frame construction, the engine was considered a stressed member of the frame and had to be included in analysis of the frame's structural integrity. At the time, Kawasaki did not possess the resources necessary for computer analysis so gruelling test-rides of hundreds of kilometers per day had to be carried out, again and again. After various trials, it was decided that high tensile steel pipe would be used for the main frame and aluminium square pipe for the seat rail. An Automatic Variable Damping System (AVDS) equipped 38mm front fork and a rear UNI-TRAK suspension system, together with the 16" front and 18"rear wheels, completed chassis development and provided the GPZ900R with light handling and excellent stability.
GPZ900R frame
UNI-TRAK suspension system
AVDS
With the frame nearing perfection, it was time to delve into fairing design. At a time when 1,000cc motorcycles were the main market forces, Kawasaki was working to topple them with a 900. So of course, the perfect design was required for the "next-generation, Supersports machine." Research was conducted from the dual aspects of great design and aerodynamic efficiency. While maintaining 'good looks', every part had to be produced in a manner that enhanced top speed. Illustrations were based on the slant-nosed appearance of a 'jumping dolphin'-like image. But in the end, the dolphin silhouette had to be toned-down due to market trends that were rejecting anything extreme. Many proposals were made and finally the uniquely modem lines and angular appearance of the GPZ900R were finished. Numerous wind-tunnel tests were made to improve aerodynamic characteristics as well as design quality. The resulting coefficient of drag was a surprisingly low 0.33.
Eleven years after the introduction of the Z1, Kawasaki's newest 900cc could again claim the title "World's Fastest." Its recorded top speed was over 240km/h and its 0-400m acceleration time was 10.976 seconds. After tireless preparation, Kawasaki introduced the new GPZ900R to the public at the 1983 Paris Salon. Its outstanding performance capabilities utterly impressed all who attended the GPZ900R world press introduction at Laguna Seca Raceway, USA in December of the same year. In January 1984, sales of the GPZ900R began world-wide with the word "Ninja" added as a prefix to its name for the North American market. It didn't take long before the GPZ900R became the best-selling bike in the world. It won the title "Bike of the Year" in many countries. Since being introduced 13 years ago, more than 70,000 units have been shipped from Japan despite the GPZ900R having yielded its Kawasaki flagship position to the ZZ-R1100 in 1990. Today, in 1997, 25 years after the Z1 and 13 years after the first Ninja, Kawasaki will see a new entry to its high-performance 900cc legend........(to be continued.)
