by Cornelius Vanderheuvel
ISBN: 0760304106
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An excerpt from the book "Pictoral History of Japanese Motorcycles" by Cornelis Vanderheuvel (a Dutchman). Models are often introduced to Europe and Australia before the USA, hence the 1972 mention.
"There is a Yamaha model range that started in 1970 and lasted until 1984. The XS650 has its own chapter. The XS500 adds up to a difficult story for Yamaha. In the early seventies Yamaha had no answer at all to the Honda CB500 four, the Suzuki T500 or Kawasaki's 500 Mach 3. The 1972-introduced XS500 was, technically, an interesting bike, but drawbacks in styling, performance and reliability prevented it from being successful. The interesting part is that this double over-head camshaft twin had eight valves. This was not all new, of course, for Nourish in the UK made eight-valve heads for Triumph as early as 1968, but Yamaha was the first to have them in serial production. The bland looks of the model amounted to no more than a weak representation of the TX750 (this illustrious bike has its own chapter). A TX500 (in the USA) or XS500 (in Europe) was not a high performer. Cracks would occur in the cylinder head, from spark-plug site to exhaust valves, and between the valves. The problem was never really sorted out; and finally the model vanished. Having said that, I have seen one example really go at a classic racing event!"