1936 Bsa 750cc Model Y13 Frame no.: D13. 294 Engine no.: D13. 202 During the 1930s Bsa concentrated on producing an extensive and varied range of dependable, well-made and competitively priced motorcycles. The majority of these were singles, but for the sidecar market Bsa offered the Model G 985cc sidevalve v-twin and for the more sportingly inclined rider, a smaller overhead-valve v-twin, the 499cc Model J