I have coil and battery, so this is not about Austin 7s. On another forum, selling a Matchless with a magneto, a poster has said that retarding the spark is not necessary and in fact that the magneto produces a weaker spark when retarded. I always retarded the spark on my motorcycles to avoid kick back. But more importantly, I don't see how retarding the spark would weaken it. Shouldn't the mag produce a consistent spark but retarding just causes the spark to occur at a different point in the engine's cycle?
Erich
Erich