It simply depends on the drive system of pinions and/or chains adopted by the
manufacturer (and of course the direction of rotation of the engine). The
direction of rotation of a magneto is traditionally referred to as being
clockwise or anti-clockwise when viewed from the drive end, not the contact
For a bit of fun, we've put together a set of schematic drawings of the
timing systems of a few 1950s British motorcycle engines. See if you can guess
which engine is shown, and then press the reveal button to check.