ranks
New member
Came across this little tidbit here about development of the TZ750 and YZR500:
http://www.mcnews.com.au/features/2003/YZR_History/Yamaha_YZR_History_Page1.htm
Retired Yamaha engineer Takashi Matsui recalls the start of the development project: "We were intending to eventually participate in the GP500 class so we started work on a 500cc model, but at the same time we had our eyes on Daytona. So we started developing a 700cc models simultaneously, calling the 700cc the "YZ648" and the 500cc the "YZ648A." By October of 1971 we had completed three prototypes to the point where they were running fairly well. Then we spent all of 1972 developing the finer details of the machines, which were now being referred to by their development code names "OW19" (700cc) and "OW20" (500cc)."
A number of innovative features were developed during that year. "In order to get a much slimmer engine design, we grouped the four cylinders into units of two each and then introduced an "idle shaft" between the right and left crank shafts as the drive force shaft. The enabled an engine width about the same as a V-4. And to make the overall design even more compact, we fitted the ignition system in the space on the non-drive end of the idle shaft axis," adds Mr. Matsui.
"From our experience developing the RD05 (the 1964 250cc GP machine) we learned that the ignition order has a big effect on the idle gear, and so we decided to use a well-balanced firing order in which the two inside cylinders and the two outside cylinders fired at the same time.
http://www.mcnews.com.au/features/2003/YZR_History/Yamaha_YZR_History_Page1.htm
Retired Yamaha engineer Takashi Matsui recalls the start of the development project: "We were intending to eventually participate in the GP500 class so we started work on a 500cc model, but at the same time we had our eyes on Daytona. So we started developing a 700cc models simultaneously, calling the 700cc the "YZ648" and the 500cc the "YZ648A." By October of 1971 we had completed three prototypes to the point where they were running fairly well. Then we spent all of 1972 developing the finer details of the machines, which were now being referred to by their development code names "OW19" (700cc) and "OW20" (500cc)."
A number of innovative features were developed during that year. "In order to get a much slimmer engine design, we grouped the four cylinders into units of two each and then introduced an "idle shaft" between the right and left crank shafts as the drive force shaft. The enabled an engine width about the same as a V-4. And to make the overall design even more compact, we fitted the ignition system in the space on the non-drive end of the idle shaft axis," adds Mr. Matsui.
"From our experience developing the RD05 (the 1964 250cc GP machine) we learned that the ignition order has a big effect on the idle gear, and so we decided to use a well-balanced firing order in which the two inside cylinders and the two outside cylinders fired at the same time.
Last edited: