Making SPARKS FLY

This being an article about magnetos, it will not say much about the coil ignition that became commonplace in the 60s, with the arrival of alternators . However one thing that should be apparent from the 'high tension coil ignition' diagram is that there is almost nothing to it, and the only moving parts are the cam and contact breaker lever - especially when a bobweight ATD (automatic timing device) provides the advance retard function. That means very simple fault finding.

Mechanically, the cam needs to be snug in its bearing or bush (10 thous of slack will wreck the effectiveness and timing of a 12 thous opening!), and the moving point needs to move easily on its pivot but not be sloppy, or the pivot wobbly . Electrical fault-finding is simplicity itself, and a simple instrument bulb wired to a couple of croc clips is better even than a testmeter. terminal to earth. Points open it