I linked my battery drain on my 62 to the ignition switch. When I opened up the ignition switch, I found green corrosion and original 1962 grease. I cleaned up the contacts and lubed the switch lightly with fresh dielectric grease and reassembled it. For what it's worth, I have a .5 volt drop from the ignition switch to the battery when the bike is running at idle. I'm better at nuts & bolts than contacts and volts, so I don't know if a .5 volt drop means anything.
I keep my battery fully charged because I take frequent short rides, just to be on the safe side.