@2M: plugs are ok. They've only got maybe 300 miles on them, maybe a bit too dark, but I had been doing a lot of low RPM cruising and sitting at idle. These are standard copper BP7s.
@MaxPete: Any given speed required ~300 fewer RPM. With proper timing, each combustive event provides more power thus requiring fewer of them. Following the timing adjustment with the light, I observed that it required about 300 fewer rpm to cruise at given speeds.
@5twins: I've been reading up on the reg/rect upgrades you and a few others did. VR-115 and a couple diy bridge rectifiers.
I'm thinking the rotor is ok. 5.5ohms ring to ring, no continuity either ring to ground. Everything in there looks ok. No hint of previous overheating. Stator wire bundle nice and intact as it passes the drive sprocket.
I am finding a .6v drop from battery voltage at what I take is supposed to be the brown wire. The one on the brush with only one screw? It's green on my bike, but it's the only one getting voltage between it and ground. The other, 3 screw, brush is attached to the longer black wire and sees no voltage between it and ground.
I had thoughts of doing a complete electrical rebuild from scratch someday hence. As my daily ride, through sometimes heavy traffic, I'm leaning toward the reliable, low rpm full voltage charging of a PMA. How much does it make sense to dig deep into upgrading the stock system if a PMA was already on the sort of distant horizon?
Update on the rest: New rear tire and brake shoes installed. Whoa, that's a big nut on the drive sprocket!