In the end all our technical problems delayed the roll out by more than one year But we had succeeded, XT was now more reliable than a big single 4-stroke had ever been. We did make this choice instead of using a one-piece forged crankshaft with assembled connecting rod because it allowed us to build a much more compact engine and was also cheaper to produce due to its vertically split crankcase. The con-rod had no big end bearing but was turning on a needle bearing that needed a low pressure lubrication. At that time we didn't even try balancer systems, although we had many problems with broken crankshaft bearings as well. We even had a cylinder that broke in the middle. Cylinder and head development was as difficult. We tested many different configurations including DOHC and even cylinder head oil cooling, but the XT was supposed to be simple and reliable and we turned away from all these complicated solutions.įirst, the heavy pistons gave us countless problems. It was only the second four-stroke designed by Yamaha. Nakamura-san continues, "Now I can confess that developing this first big single was a real nightmare. As soon as they had a bit more power they turned out to be unreliable and they were shaking like hell." Honestly speaking, we engineers were quite reluctant in the beginning, since we knew about the difficulties of these big thumpers. Soon the sales guys started to request the development of a four stroke for off road. Shiro Nakamura (later also responsible for XS 750 triple, XS 400 twin, XS 1100 four and the SR 500) who developed the XT engine remembers: "When the off road market started booming in the US, bikers remembered the advantages of the good old singles. No wonder the world was kind of shocked when the forgotten came back: the XT 500 brought back the steam hammer sound of a big single four stoke- and the world was prepared to listen. They were less vibrating and so much easier to ride and the breed of big thumpers seemed to share the fate of the good old dinosaurs. The famous British 4-stroke singles, such as Norton, Velocette, or BSA had died, smoother and faster bikes, replaced them. Forgotten were the times in the sixties where big singles touched the heart of enthusiasts. It was a fascinating development and most manufacturers did everything to boost this mainstream fashion, when Yamaha turned around and seemed to go backwards. The dream was made of multi-cylinders with constantly increasing horse power. The roaring seventies saw a breathtaking development: faster, bigger and heavier, the motorcycle world seemed to turn around. Although, the reputation of the SR500 remains so strong, that Yamaha has continued to produce it both for the Japanese domestic market (in 400cc form to take advantage of registration laws) and for the European market where its popularity has never diminished. The SR500 eventually led to the SRX600 and Yamaha now produces a 660 road single. Released in 1978, the SR500 was Yamaha’s attempt to cash in on nostalgia for the period when 500 singles were the preferred mount of serious riders. 1.6 The XT 500 in the Paris Dakar rally.1.4 SR 500: the thumper for the open road.1.2 Many technical problems to be solved.
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