Yes, start by checking the brushes. they are considered a wear item and once worn too short, they can lose good contact with the slip rings. Charging output will drop off or even quit completely. The outer slip ring that's showing doesn't look real dirty. Usually the carbon rubbing off the brush turns the ring black. In this pic from my '78, I've cleaned the outer ring but haven't done the inner yet .....
I think it's best to remove the stator for slip ring cleaning and measuring, and for brush inspection. It's easy, there's only two screws holding it on. Just be aware that there is a small alignment pin at the bottom you'll need to line up for the stator to fit back on completely. You can just swing the stator over to the side and rest it on some wood blocking like so, no need to unplug the wiring harness. This pic also shows what I like to use for cleaning the slip rings, just plain old chrome polish. After cleaning, I wipe the surface down with electrical cleaner to remove any polish residue ......
As I mentioned, your slip ring that's showing doesn't look real dirty, but I am a bit concerned about that silver color on it. That brush may be worn right out and you have metal rubbing on the ring. New brushes are about 14.5mm long and the wear limit is about half that, about 7mm. If it's a factory original brush, there will be a wear indicator line etched in one side .....
OK, after you check the brushes, the next thing to check is the rotor. To do that, you measure the resistance between the two slip rings. You want to find about 4 to 5 ohms. Unfortunately, rotor failure is pretty common. It's not a bad part really, it's just 40+ years old, lol, so they're crapping out. If yours is bad, the best course of action is to have it rewound. There's a forum member who does them and he does a wonderful job. You can buy new aftermarket ones but the quality is hit and miss.
The regulator and rectifier aren't connected. The regulator feeds voltage into the rotor to make it charge. The AC current the stator and rotor produce is sent to the rectifier and it converts it to DC current that the bike needs and uses.
, so I have a "loaner" if you'd rather not buy one. Also have a rotor ready to go currently. Lemme know...
