Yamaha XS650 Development History - article

[Wolfchen]

I was curious about the first XS1B 650s and used search but didn't find anything specific on the bike's primary development.

Here's a more detailed account of the successful factory effort using SOHC valve technology from Toyota. Ford used a Yamaha designed 3.0 liter engine in their now famous SHO V-6 and 3.4L V-8 engines.

http://www.classicyams.com/street-bikes/4-stroke/yamaha-xs1-development-story.html

There was another article about Yamaha engineers initial disappointment with the engine's low power output and how it was dealt with but I'd lost the text.

 

[grizld1]

The XS650 engine bears no resemblance whatever to any other Yamaha 4-stroke engine because Yamaha didn't originate the basic design. The engine is essentially a punched-out Horex 500, the design for which Yamaha acquired when they bought out Showa (a defunct motorcycle manufacturer, not the suspension manufacturer), who bought out Hosk (a short-lived maker), who bought out Horex, a German firm, when it went broke in the 1950's.

That development story has been around for a long time. It emphasizes the few details worked out by Yamaha engineers and avoids any mention of the origin of the core design from which they worked. If you want some insight into how much of a clue those engineers initially had when it came to large displacement 4-stroke cylinders, talk to some oldtimers about the needle bearing wristpins that went into the first few XS1's. Those heavy 4-stroke power pulses ate 'em right up.