NEXT MORNING: The charger (really a battery maintainer) said it wasn’t fully charged yet, but I went ahead and disconnected the charger and tried the starter, and yes, it started. I wasn’t sure if I’d have a problem, considering how long I had let it sit.
But… the vacuum petcock must leak down a bit, as the airbox seemed full of gas, which blew out onto the cardboard I use to protect my garage floor. Ick. Pulled the bike outside, threw the cardboard in the trash (it’s trash day so it won’t sit around here for long), and let the bike warm up.
Ran it down the road south out of town, up over the 6,000 RPM mark, and no slipping. Killed it in my driveway on the return; clutch was dragging a bit, and I realized I must have loosened the clutch lever adjustment when I first discovered the problem almost two years ago. Corrected that, and am now happy with it.
Still hate that Michelin Commander II. It’s going for sure; the rear looks like it’s ready for replacement, so maybe I can get something I like better.