My car was running rough. I did all the easy stuff to check it out, eg checked coils, visually inspected timer and wires, cleaned carb, tested plugs, tested continuity, etc. I eventually found a short in the #4 commutator wire and replaced the wiring. No dice, problem still persisted. I finally took the timer off to inspect it. (No easy task for a 1910 two piece timer.) There I spotted the problem. There was a burn hole in the plastic part of the race near the #4 terminal. Evidently the short in the wire somehow make a track to ground. Can't really explain how or why that happened, but when I replaced the timer body, it ran like a charm. Go figure!