Hi Bruce, Yes both taps are on, it doesn't have a tickler I have a 1982 model with a choke, haven't checked the float or float level, haven't cleaned out the various jets ,wouldn't really know where to start (i'll have to get a workshop manual).From my experience with my SS with 40mm carbs it's often the front one that plays up. As well, the fuel flow to that carb can sometimes seem to be a mystery. Do you have both taps on? Does the tickler on the front carb flood it whenever you press it? Have you checked the float level? Does the float move freely? Have you cleaned out the various jets, air passages and filters?
I would normally check the carbs first as well, though you did mention it started to run better when cleaning and swapping the spark plugs. Like someone else said, the boots can get cracked and let air in as well so check those (if you have any suspicions, use electrical tape and wrap them to test [not usually a smiled upon long term solution, but easy to verify and easy to remove]). I would check the float height in the carbs, it looks like the link Roadstar gave you is a great starting point for the whole carbs in generalCheers Greg,
The Dellorto tuning guide at the bottom of this website will pretty much tell you anything you need to know about these carbs. It is downloadable. I'm inclined to believe you have a fuel delivery problem rather than an electrical one - I've been there. Having said that the pick-up wires should be replaced as a matter of course if they haven't been already because this is a notorious trouble spot that affects all these bikes.