Bert, I copied this from the comments in the gallery:
June 17, 2011, 06:44:34 AM
Sounds like there is a fair bit of confiusion around the "EJR" racers. The figures for power output were taken form a Japanese book "The History of Japanese Racing Motorcycles", published back around 1980. Although the book is written in Japanese (which I can't read) the quote of 13.5 HP at 16000 rpm was taken from the caption on a photo said to be of an EJR1. That bike has a different shaped fairing compared to the EJR2 pic alongside it, and no sign of a radiator, so I assumed it was the single.
The 50cc twins appeared in two colour schemes (1965 and 1966) with identical shaped fairings. I believe the early twins had a 10-speed box, later changed (I think) to a 14-speed unit. Presumably that accounts for the two versions of the twin that you mentioned.
When the roadster BS50 Sport was released in 1965, Bridgestone did produce race-kitted versions and raced them in the Japanese National series. These produced around 10.5 hp at 13,500 rpm. Of course these would have had a right side carb, and the motors would have been clearly derived from the road bike.
Maybe Bridgestone did produce some early prototypes singles with left-hand carbs, but I wonder if they really would have produced them as early as 1963. After all, at that time the BS90 hadn't yet appeared, and their main product was the BS7 and Homer (both piston ported motors)
Your pic was the first time I'd seen a pic of a left hand carb air cooled single without a fairing, but it seems there is much more to these Bridgestone racers than meets the eye.
Thanks for your reply.
Graham
Link:
http://bridgestonemotorcycleparts.com/index.php?action=gallery;sa=view;id=690