Good question John… I suspect that those very energetic (like 6000V) electrons just see the gap (s) as high resistance obstacles. Now if the gap (at either end) becomes too great, as in spark plug wire disconnected we have a real problem because the high voltage WILL find a way to make the circuit and likely it will be somewhere internal to the coil… not good! The same issue as "never pull over an engine with out grounding the spark plug wire". On an opposed twin, don’t even leave one of the plug wires ungrounded, if you value your coil.
Joe B
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