I might mention that the 2 bosses on the frame where that clutch-cable-ground-bracket thing mounts should also be bare of paint so the engine's non-starter-related switches (Neutral and Oil PSI) can ground easily. Otherwise their lights can be dim when ON.
The way the OEM voltage regulator works is: it is fail-safe, but 50 years of life (being 40 years more than Honda planned on) have let the upper contacts inside it corrode a little bit. This is easily removed with a points file: just remove the top cover of the regulator and slide the points file in between the 2 upper contacts and give it a few polishing whacks (and clean the debris away). That's all it takes to restore most of the regulators to full performance.
Measure the 2 wires to the regulator's field coil to make sure they are actually connecting. The little bullet connectors are corroded by now on many of them, causing low (or NO) current thru the field coil. which reduces the charging power from an already-smallish alternator. While Hitachi rated the design at 120 watts, most only makes 90-100 watts because the battery voltage is typically on the low side (especially in the USA where the lights must always be ON while riding). Once below 11.8 volts or so, it can seldom catch back up unless the bike is ridden for a long time with the lights OFF, or the battery charged up for a time.
