850 Norton Right Cylinder Misses

Nicholson says 5/16" for 750/850 Commando with 28° advance. Sounds close to an Atlas with 11/32" @ 32° If you're trying to account for the angle of the plug hole none of the above will be correct. Jeltz clamps a piece of small diameter welding rod to the end of the dial indicator so it's vertical. Repeat tests against a degree wheel show "close enough" for me.