Going in circles chasing electrons...

[edthetermite]

If you ever do electrical work on your bike like cleaning up loose wires or eliminating wiring no longer needed it is a good idea to make sure you don't forget your ground system. I have been chasing down a non-charging electrical system for longer than you will ever know. The simple things should ALWAYS BE CHECKED FIRST! The rectifier/regulator ground wire terminates on the frame with the battery ground. You can't see it because it is hidden behind the battery on one side and the air filter box on the other. The only good thing out of all this is that I can now thoroughly check my charging system out. The Snidal troubleshooting techniques were all put to use on this one. I understand things a lot better now but it is still embarrassing as to what the problem actually was. Live and learn.

[Arizoni]

The problem with chasing electrons are they are so tiny their hard to see.
They are also sneaky and can all join hands and look like they are happy but as soon as you turn your back they let go and start taking naps.

Then there are cases like yours where a perfectly good looking wire can decide it doesn't like the surface its supposed to be contacting.
These will often collaborate with their old buddy, corrosion, and build a barrier between themselves and some ground location or another wires connector.

Glad to hear you found their latest attempt to quit working.

[edthetermite]

It's nice knowing I have a new battery and the ammeter needle  once again wandering to the right on the gauge face. If it stops showing a charging condition for very long something is up. Your battery, if in good shape, and you keep the headlight off and stay off the brakes and horn will get you a considerable distance before the coil stops working. Easily over a hundred miles.