Went for a drive yesterday. While well under way and cruising, the engine went silent for a few seconds and then came back alive.
A little while later a second issue was it felt like I was losing power but the engine still running. I switched to battery and the power came back. I then switched back to magneto and it ran fine.
With these issues and symptoms what do you think is going on and what should I start to troubleshoot?
The signs of a weak magneto would be the engine would not run at idle or low speed, but would run OK at faster speed. If you slowed when it happened or maybe were pulling a hill or idling when it happened, it could be a weak magneto. If it seems to happen mostly when you pull a hill or when you shift to low gear, you could have excess crankshaft endplay which would move the magnets farther from the coils inside the magneto. Also, you may notice that there are certain points on the spark lever quadrant where the engine runs smoothly, but when you either advance or retard the spark it runs rough, you could have a problem with the timer. In that case, you could have one or more cylinders running at more advance or retarded than the others. This could happen with a bad timer, or if the timing gear cover is not centered.
Another problem giving similar symptoms would be a loose connection at the ignition switch, the connection block or the timer plug of the red wire.
Lastly, the problem could be the contacts inside the ignition switch itself.
Remove and check the mag contact for a good connection