I saw a recent thread on the VMCC forum and I know MM isn't on there any more so thought I would report some details on here as it is a good example of lots of things on this thread about poor mag rebuilds.
A guy was having trouble with his magneto so sent it to a re-builder to fix. The re-builder reported back that:
"There were 2 wires, seemingly from a wire brush, inside the armature, the wire from the winding was not in good shape, the screws which hold the armature together were the wrong thread and although they seemed tight, they would very quickly become loose.The condenser was wrong and did not fit into the space available, so it had been shoved in at an angle and the wires coming from it were bare. All of these thing would cause a problem so to have them all.... no wonder the bike would not start."
I know there are reports of poor mag re-builders but whoever did this must have had zero sense of shame.