BSA’s parallel twin was both inspired by and intended to compete with Triumph’s Speed Twin. The latter was - as you know - famously designed by EdwardTurner. What you may not know is that the same Mr Turner worked for a while on the design of BSA twins while employed by that company for a couple of years from 1942. If you’re feeling enthusiastically anorak, Signs Of Turner can be found here and there in the early 500 twin engine, the A7, including Triumph-style screw-in rocker adjustment covers in
