A common source of engine trouble
We have probably all known or experienced engines with a temperamental personality. They either start hard or else, once started, run very poorly. Taking into account the time period in which these engines were built, their age, and level of technology, a certain amount of eccentricity is to be expected.
I did not expect such a situation, however, with my recently restored 2-1/2 HP Stover (CT-2). Knowing it had been restored perfectly, I expected it to smoke on the first try. Imagine my frustration when repeated attempts produced nothing but blisters, a profusion of sweat and the near surfacing of a new vocabulary. A little diagnosis revealed the cause to be a weak to nonexistent spark from the WICO EK magneto.
Having recently been overhauled by Richard Eckert, a well known and respected rebuilder of magnetos in Prescott, Arizona, the chances of this magneto being dead seemed unlikely. The substitution of two different EK magnetos from well running engines did not fare much better although the engine finally started and would run momentarily but roughly.
Returning to the original magneto, a quick resistance check verified that the primary and secondary coils were in good condition with no open or shorted coils, and no shorts to ground. The condenser was not shorted either and the points were clean and breaking properly. The magnets seem plenty strong. Opening the pole piece manually produced a nice fat spark every time but it would not repeat when installed on the engine. Hmmm........
Finally the engine started but ran roughly just as it did with the substitute magnetos. While watching the mag with its side cover off and the engine running, I noticed a profusion of sparks between the movable point and its bore. It obviously was not adequately grounded. When the moveable point was shorted to the side with a screwdriver, the sparks stopped and the engine immediately started hitting regularly and running smoothly.
High tension ignition systems depend on grounding of the points to complete the primary circuit. A quick analysis of the WICO EK reveals that grounding the point is shaky at best because it is not only moving, but in varying states of lubrication. Arcing between the moving point and its bore is likely to result in increased wear as well, because of pitting on the sliding parts. Other parts of the path to ground are the clevis pin and clevis lever, the ignition point screwhead, and the magneto bracket. Again, this is a pathway of lubricated moving parts, corroded or freshly painted surfaces.
It appears to me that the ground path is a weak area on all WICO EK magnetos and could be a major contributor to cantankerousness of any engine on which it is used. Recently cleaned and painted ones will most likely be worse because the problem is compounded.
To fix it I used a short length of small braided copper strap and soldered electrical eyelet terminals to it. I ran it from a magneto cover screw to the clevis pin nut. This strap insures a good continuous ground for the primary circuit. (NOTE: The small braided copper strap is readily available and sold in electronic stores as "Solder Wick" or "Wick Up" for desoldering electrical components.)