Reply To: '65 BigTwin 40hp 1/2 spark

[Don]

Jeff, your discussion about one system/cylinder’s components somehow interacting/affecting the other cylinder’s ignition components is very intriguing indeed! Just wish I could understand your theory a little better….
You point out a very important issue though, mag plate slop, no matter what might be causing it, will affect point gap and coil air gap, perhaps to the point of misfiring.
Finally, it is only in recent years when I have gotten into the habit of “reusing/cleaning up old points” on engines used infrequently, that I have noticed excessive rubbing block wear and pay more attention to spring tension. I never paid much attention to these issues in my younger days because I never reused points/condensers.