It wasn't just for motorcycles. The threads were called British Standard; fine threads BSF and the coarse threads, BSC. All Brit stuff, Cars, motorcycles, airplanes, etc. used these threads until about the late 60s they started to convert to metric. A lot of stuff built during the conversion stages of several years, would have a combination of the two threads, that is British standard and metric. Of coarse, the spanners were different than anything else, too, and the BSF and BSC spanners were different, too!
Fun times working on Brit bikes and cars in those days.
Bare