BSA’S unit-construction single-cylinder engine might not have had the iconic allure of the pre-unit Gold Star, but it proved competitive in its day, predominantly as a lightweight motocrosser but also in road racing (especially endurance racing) and, of course, formed the basis of several peppy roadster models. The thumper grew in capacity from 350 to 440cc, and finally to the 500cc B50. When BSA closed, the remaining B50s were rebadged as Triumphs, but good as any of the Bsa/triumph production bikes might have been, they had so much more to give. This was proved when we tested a prototype BSA had been developing using the Isolastic system Norton used so effectively on the Commando range. One of the many things we discovered this month was that despite Yamaha’s supermoto-styled TDR250 being initially considered totally impractical, it’s every bit as much fun to ride as it’s TZR racer-style sibling. But debunking old prejudices is part of the joy of revisiting old classics.