Are you sure the plug wires are on right 1-3-4-2 ?
If a valve adjustment is too tight on that cylinder it will fire when cold but as soon as it heats up the valve doesn't make it quite closed and it loses compression and skips. Also when those flat heads blow a head gasket it will leak between two adjacent cylinders. I would get it hot and do a compession check.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.