Speaking to a chap at my YAMAHA Parts Distributor FOWLERS of Bristol yesterday, he told me of a story regarding why the FS1 was reintroduced into the UK by YAMAHA in the late 80's.
Apparently a YAMAHA Dealer called Rafferty Newman bought all of YAMAHA's remaining European stock of FS1-E spare parts as the model was being discontinued. However YAMAHA Motors Europe forgot to switch off YAMAHA's automatic re-stocking ordering system and all of the parts were then re-ordered from Japan. By the time they realised it was to late to cancel and it was then decided to relaunch the model in order to stimulate demand for all of these parts they now had in stock .
Sounds plausible enough I suppose as a lot of the Rafferty Newman left over FS1-E parts have recently come to light and has been sold off at the various bike shows and jumbles? I bought a fair bit of it myself and was also offered a job lot of it recently