Whether because of aging of the windings, the use of electrical loads greater than wsa typical when the bike was designed, or simply a pattern of riding that is not sufficient to keep the battery at top charge, it is often beneficial to slightly increase the charge rate of the 1970s vintage Honda SOHC Four having the early style adjustable vibrating point regulator. The factory built the adjustability into these regulators, so it is there to do if warranted.
And warranted it should be before you do it. There must necessarily be a few caveats. First, before deciding the bike can't keep its battery charged, make sure the battery is quality. If you're getting your bike batteries at Pep Boys, well, you know what you've got. You're not likely to have the best battery experience with that kind of battery. In any case, charge the battery, then hydrometer test it, then load test it. If this to you is too much trouble, then go back to being a couch potato and thanks for sticking with me this far anyway.
Once the battery has passed a load test, test charge to the battery. Do this in amps, not volts. Follow the guidelies in my SOHC Charging Troubleshooting article and pay special attention to the keyswitch and the many electrical connectors. Once you have determined the system is operating the way it should, you're ready to tinker with it, but not until then.
Many folks have espoused using a meter and measuring output while at a certain rpm, etc., etc., but my method for upping the charge rate by adjusting the adjustable type regulator is simple, just like the factory's (below). I simply note the number of threads visible above the locknut, usually it is seven or eight threads. Then I loosen the locknut, and turn the screw inward until half that many threads are showing, that is, three or four, and tighten the locknut, taking care the screw does not turn with the nut. Below is a sample of the page from the 69/70 CB750 factory service manual describing this same procedure.
Some on forums have suggested that the regulator should have its core gap adjusted. I don't at all recommend that. Unless you know for sure someone has been monkeying with it, don't you be the first monkey!
You will want to monitor the electrolyte (water/acid solution) in your battery for a while, especially in warm weather or on long rides, after doing this. If the level drops more frequently than you find acceptable (despite what some forum "experts" contend, water loss of some kind is normal), then adjust the screw back out one thread, see if that fits your riding pattern better, and so forth. Enjoy.