Thanks for the kind words mspa! I enjoyed the company of both you and your friend. Having you around reminds me of my early days with these airheads - and it's satisfying filling you in on all the things that took me so long to find out.
I've got a new adjustable voltage regulator you can have for $22. So that's not a problem. Since yours is working, no rush on that. Pick it up next time you're down this way.
I agree with Disston - at this point there are two possibilities for the clutch - out of spec pressure rings or lube on the disc. No way to know which till it's apart. Fingers crossed it's lube...
All the fasteners on these bikes are metric, so 5/16" aint it.
And no split lock washers either!!! Only wave washers!
You'll need the 8mm nuts ( 13mm wrench) for the bar clamps. But there's no rush - with the nuts sufficiently torqued, they won't be coming loose. They've managed to stick around, what... 34 years? now. I don't think they'll be going anywhere but where you take them.
I assume the speedometer (and odometer) have been working ok? You asked if it needed parts - no. But the odometer was so sloppy it's a wonder the number wheels weren't flopping all over the place.