Thanks to all that replied about spark plug gap theory.
Having explored the maximum+ gap region, I am now trying the minimum gap for comparison.
For the last few years, I have used fine wire plugs on the bottom and massive electrode on the top. The fine wire plugs are much more forgiving of crud build-up.
A note about starting with EI vs. magnetos. Unison makes a device called Slick-Start that uses battery power to help the magneto during start-up. It produces several sparks per combustion cycle with a lot more energy per spark. The engine starts on the first attempt - every time, regardless of how badly the priming was mis-judged.
Chris Zavatson
N91CZ
360std