Thanks for the replies. Really appreciate all the info and the helpful advice on this site.
Here she is. Not all that much to look at but it sure is fun to ride; it'll be even better when this little power issue gets solved. The yellow is kind of loud and the paint job isn't high-quality but it got a nice shine to it after a little work with the polishing compound and wax. The PO put a F-style side cover on the right and couldn't understand why it didn't fit right...
Anyway, I've done a lot of the basics (points adjusted, valve clearance, plug gaps, cleaned gas tank strainer and petcock screen, fork oil, engine oil, added carb drain tubes, adjusted drive chain & timing chain, moved the battery ground connection to where it belongs, synchronized carbs, changed brake fluid, etc.) Still need to remove/inspect/clean the carbs but I'm putting that off until the last of the riding days are gone this year, probably during Christmas vacation.
MD: that's a great tip! I have not tested or even inspected the plug wires & caps. I'll do that tonight. And yes, the power loss is when the engine is fully warmed. It seems worst when I just try to slowly roll into the higher revs. It just hesitates and sloooowly revs up to max of 4500 or 5000. However, if I'm aggressive going through the revs and gears, the engine will get up above 7000 and feel strong as long as I stay there (which isn't usually that long; I'm mostly a casual rider).
The electrics on the bike seem solid. I've had no problems with the battery or using the starter and all the lights work, etc. So I don't think it's a charging issue. But maybe the coils & caps... great hint!