First blush of a charging issue….

[kidsmoke]

93 1000S mid valve.

New to me bike. Somewhere along the way on the first real ride, a splendid 323 mile day, as opposed to the (many) 20 - 30 mile runs preceding that, the charging light decided to stay on. I also began to experience rare/LOUD backfires, usually rolling off the throttle slightly.

Disconnected the headlight and made my way home (66 miles)

After getting home and pulling the seat, I noticed the positive post screw was very loose. Tightened it up and put it on the charger.

This bike has the Ducati voltage regulator and digiplex ignition.

On the lift, When putting the meter on the battery, at rest it reads 12.6 and it shows a steady 12.3 volts at 3000 rpm, and the light stays on steadily with no hint of fading.

Assume I know nothing. I won’t be offended.  What do you think is occuring and how shall I begin chasing it down?

[Frenchfrog]

Sounds like it could be the regulator.I'd assume that the backfiring was due to low battery voltage at this point...you should be getting more voltage at revs than that .

[kidsmoke]

Adding the detail that varying revs, up to 5k down to 1500 k, no variation in reading

[moto]

I might start by checking the health of the battery. You can do that with a load tester or by taking it by a battery store. I think all other tests depend upon having a good battery.

[berniebee]

You should be seeing at least 13.8 volts, but ideally 14.0 to 14.5 volts at 3,000 rpm with a fully charged battery. The regulator might not be grounded properly. If you have a lead with alligator clips, you can quickly test this by attaching one end of the lead to the regulator body, the other end to a bolt on the frame or a bare spot on the frame . In other words you are providing an alternate ground.
 
See if the charging voltage increases with the lead attached. If yes, shut everything off and clean the regulator to frame connection to ensure good contact.

[PeteS]

A shorted cell in the battery would bring charging voltage down but then it wouldn’t read 12.6v with the bike not running.
Its a regulator issue or bad connection, just not sure what the problem is with these.

Pete

[chuck peterson]

Dr Dave Richardson’s idiots guide to guzzidom got me thru

Have fun!

[Chuck in Indiana]

Agreed that the backfire was probably low voltage to the Digiplex. I'd first check the alternator with the regulator unhooked. If you have roughly 40-50 volts ac between the yellow wires at 3 or 4 thousand, it's ok. At that point, it is most likely the regulator or regulator ground.
Somebody that actually knows something.. paging Kiwi Roy.. Kiwi Roy to the courtesy phone, please..  will be along.

[Kiwi_Roy]

https://www.thisoldtractor.com/guzzi007/schematics/1991_1000S.gif
Make sure the regulator case is well grounded and the red/black wire is at +12 Volts with the key turned ON
I am suspicious of the Red wire going to the alternator, usually the red wires connect from the regulator to battery.
the red/black wire acts as a voltage reference and powers up the regulator when the key is ON
I have sometimes powered up the black lead of the regulator direct from the battery to make it charge, you could try that as a test.

[blackcat]

Same thing happened on my 93-1000S, backfiring first then pulled the light and made it home. 93's were known for having bad voltage regulators and I just replaced mine. As above, I'd make sure the battery is ok and VR is grounded before ordering a new one.

[kidsmoke]

Thanks everyone for the feedback.

https://www.thisoldtractor.com/guzzi007/schematics/1991_1000S.gif
Make sure the regulator case is well grounded and the red/black wire is at +12 Volts with the key turned ON
I am suspicious of the Red wire going to the alternator, usually the red wires connect from the regulator to battery.
the red/black wire acts as a voltage reference and powers up the regulator when the key is ON
I have sometimes powered up the black lead of the regulator direct from the battery to make it charge, you could try that as a test.

Roy, I did download that schematic. some key differences between the 91 and 93, both the regulator and the ignition are different, (as well as the engine and fueling) so the schematic may vary as well? Thoughts?

Same thing happened on my 93-1000S, backfiring first then pulled the light and made it home. 93's were known for having bad voltage regulators and I just replaced mine. As above, I'd make sure the battery is ok and VR is grounded before ordering a new one.

Planning to check both of those. Went ahead and dropped the sump to give it a quick change and ran into other issues I need to address before any RPM's can happen. Always fun uncovering PO's, ummmm, habits....

[Chuck in Indiana]

Habits..  er.. yeah. When you have done as many barn finds as I have, you will have discovered *many* ...habits. One of which is apes that shave so you can't easily discern they are actually apes. (Pete content) 
I bought a nice looking airhead one time (bad idea, but I digress) where I had to replace *every* fastener the previous gorilla had touched, including tappet adjusting screws/nuts. Broken fairing where he tried to remove the oil filter. There were others. You get the idea. 
You've got this, Kip..