I'm thinking of replacing a lawn mower Magneto with a car ignition coil. The coil would be energized via a relay in series with a reed switch in front of the existing magnet on the flywheel. Was hoping this would make the lawn mower start much easier.
I have thought of this, but it's largly unnecessary. Just get an electronic ignition for your lawnmower engine. Most older engines came with points, but you can normally directly swap with the newer all electronic modules. Huge increase in low end spark power...
Using an ignition coil would require a battery, generator to keep it charged, and still retain the points system (your relay would not switch fast enough).