Thank you SirYour alternator has been charging, but that doesn't mean that the charging system is "fine." One great virtue of the OE breaker point regulator is that it is adjustable. If you don't have a decent manual, go to www.biker.net and download the electrics section of the 1978 factory service manual. Clean points and adjust air gaps first, then try to bring charging into spec range with the output screw. I haven't found an XS650 breaker point regulator yet that didn't respond to service.
I might end doing that .I was on that a coupe of years ago .. The stock regulator overcharged warm days on the highway.
Kicking out the Boyer on one cylinder ( as I understood it ) Taking out the mechanical regulator and rectifier .Replacing with new
highway problem disappeared
Had both systems on the bike for a while the mechanical as safety. so I could plug in and out. Hazzle free last years
At this point in time I believe I have had this 11.8 at the start as system Voltage because the regulators lowered it
But have not noticed it.
Plugging in things and starting charging is there .. No reason to measure anything
I like stock .. And don't like to replace things but I could not solve it then I had three of them on the kitchen table a winter
And had a Voltage supply trying ..
I can try to service a mechanical again once I get things running and again have two setups on the bike.
The stumbling can be a intermittent short somewhere else