I removed the right magneto and harness so I could bring it home to see what's the problem. I decided I needed to run the magneto so I could see if all the plugs misfire or is it just one or 2. To do that I needed a way to run it at various speeds while watching the plugs fire.
The plan was simple create a holder for the plugs in 1-3-2-4 firing order, ground it to the magneto and spin the magneto with a variable speed drill motor.
The holder is a piece of 1 1/2" x 1/16" aluminum angle with 3/4" holes for the plugs.
To create threads, to assure a good ground on each plug, and keep the secure during testing, I used a piece of 0.025" aluminum bent 90 degrees and riveted to the angle. The threads are just a 1/8" hole with a split for it to bend like a Tinnerman nut. There is a small 1/16" chamfer on each corner. You push the plug in and turn to engage the threads. Hey it works!
I took the cotter pin from the gear retainer nut so a 9/16" socket could hold it to spin, clockwise. With the help of some adapters I got it connected to the drill motor.
You can spin it slow enough to watch each plug fire or all the way to 2700 RPM, full throttle.
At very slow speed you feel each magnetic pulse as the field builds and falls for each plug to fire. I could also see that plugs 1 and 4 fired every revolution, 2 and/or 3 however missed very often, which is why at first I thought I had reversed those 2 wires at the distributor cap.
At high speed they seemed to all fire, but not so. We took this picture while running at high speed hoping to see at least 1 plug firing in the picture. As it turns out the shutter was open long enough to get at last one full cycle 1-3-2-4. It caught 1 and 4 firing, and 4 is bright enough it looks like more than one firing. Two and 3 are not firing, which is consistent with with the firing at slow speed.
I've ordered a new rotor and distributor cap. We'll see what happens when they arrive.
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