OK, I'm going to try to answer my own question about the Bing plug. Is that kinda like talking to yourself? Grandpa said it was OK as long as you didn't start answering yourself... Uh, I'm answering!
Couple Sundays ago, a few of us airheads went for an early morning ride of just over 100 miles. Mostly went "the cowboy way". That's how we refer to Texas' Ranch Roads and Farm-to-Market back roads. No rush, mon!
We did have to giddy-up to about 60 mph on a highway leading to our nice country breakfast. This is where I noticed an anomaly in the R65s engine ops... After just a couple minutes at 60 mph, the engine revs would kinda drop off. I'd drop down to about 50 mph and the issue would resolve itself. Back up to 60 for a few minutes and it's repeating itself. Hum. My buds are rapidly disappearing over the horizon. I'm not gonna get any biscuits if I don't pony up and catch 'em.
So. A few day pass and while I'm messing with my oil pressure LED install -that's a whole other story- I removed the rather depleted RTV silicone that was slightly covering the Bing carb top plugs. Most of the old junk was not even adhering to the carb. Earlier, a local R90 guy told me that the silicone was a common "fix" for the carbs. So I used some black RTV and re-did the "fix".
This morning, I was out running errands on the bike and planned my circuit so that I would end up on our city's outside highway loop where I could test the new glue.
It worked! Ripped along at a blazing 60 mph well past the point where I had experienced the earlier power sag. Obviously, the caps really need to seal the carb chamber from the ambient atmosphere. Cheap fix. Happy camper here.
