The conclusion! The bike now runs perfectly, and everything works well. As expected, my girlfriend loves this bike, and I've put a fair number of miles on it too. New paint and less clapped-out exhaust might be in the future.
It looks like my two biggest and confusion-causing problems were a faulty shutoff switch and two backwards carb slides. I finally diagnosed the shutoff switch problem by tapping it with a screwdriver handle when the bike was running, only to have it immediately die. Any vibration or tinkering with it might cause the ignition to shut off or go back to working perfectly. I took that whole assembly apart (as I had the left-hand controls much earlier due to problems over there) and cleaned out the spider webs. I found no other issues inside there, so I think the spiders caused this problem. (They had gotten into every other tiny part, so I should have guessed.) As with the other control, the little BB and tiny springs were challenging.
As for the throttle slides, yeah, I'm an idiot. Not your normal idiot, as we've all concluded from this thread weeks ago, but an idiot with special idiot powers. When I read about the slides going only one way, I thought I had it covered by having the slot over the peg on the side of the cylinder. But no, those instructions were referring to the cutout at the bottom of the slide. However, I had adjusted the height of the slides using the drill bit method, so I think that mistake was somewhat undone. By the way, I finally diagnosed this problem after Googling and finding a couple of instances of this happening to other members of this forum.
I might also mention that a source of gas debris in the bottom of the bowls (and then into the jets) was caused by clogged float drain screws. I finally changed the gaskets on those and finally realized that there are holes for the fuel to drain without completely removing the screw. I had actually been frustrated when I thought that wasn't the case, but the passages were so clogged that the screw looked solid. I'm sure cleaning those out helped.
So this whole process was an opportunity for me to learn. From your advice, I learned that I could do this myself. Maybe my initial instinct to get professional help was on target, and I wasted a whole lot of my time. But the time wasn't completely wasted - I came away with better garage practice (e.g., keeping track of screws and parts), a better appreciation and tolerance for detail work, an understanding of CB carburetor and ignition systems, and the ability to rebuild one of these carbs blindfolded. I'm sorry if my stupid questions and side trips wasted your time too. But I assure you that your advice and support was vital in getting this wrapped up. I really do appreciate this online community.
I also learned that a bike that has been sitting for ~17 years outside will basically need everything taken apart and cleaned and lots of things replaced. And I understand sitting around outside is one big way bikes die. Maybe the biggest. So note to self and anyone else who needs the reminder: Ride your bike(s) more!
In case you're curious or considering a similar project (ideally without the ass-hattery), here are the financial details. The bike was $200. I don't know what registration cost. I wasn't much. And insurance is cheap. Total parts cost was around $800. That includes a new seat cover, speedo and tach parts, LED headlight, battery, cleaning supplies, mirrors, nuts and bolts to replace those that had rusted, most of the front brake parts, tires, voltage rectifier, points and condensers, ignition coils, spark plugs, plug wires, oil, gaskets, carb parts, fuel line and filter, air filter, signal lenses, light bulbs, clutch lever, and anything else I'm forgetting. I was surprised and happy that many new parts are available online.
As expected, my girlfriend loves this bike, and I've put a fair number of miles on it too. New paint and less clapped-out exhaust might be in the future. The bike's history (you know, before it was forgotten) is enmeshed in Yellowstone National Park, all three owners using it to get to work in the park. So we immediately got a special national park license plate as a shout-out to that legacy. I'm sure it'll visit other national parks real soon.
