T he history of BSA is very likely one of the most familiar to classic enthusiasts . Once the largest and most successful motorcycle manufacturer in the world , BSA began as an arms manufacturer . The Birmingham Small Arms ( BSA ) company came about as a result of an inadequate supply of weapons during the Crimean War of 1854 to 1856 . The arms company , comprising a collection of manufacturers , was formed in 1861 to modernise the manufacture and distribution of weapons . Bicycle making followed , but the first motorcycle didn ’ t appear until 1905 . BSA continued to produce weapons and motorcycles through two World Wars , and further . The end , for the once industrial powerhouse , came in the early 1970s . We have dealt with several BSA models over the years , from the trusty , all purpose , single cylinder 125cc Bantam of the 1950s , to the 750cc three cylinder Rocket of the 1960s . The BSA catalogue also boasts singles , and V-twins between the World Wars . After the wars it seemed the bulk of the British motorcycle industry became totally enamoured with parallel twins . Royal Enfield , AJS , Matchless , Norton , and Triumph all produced parallel twins . No doubt following the example set by the Triumph Speed Twin in 1938 . It was a template that lasted for at least the next thirty years .