And the doctor has rendered his diagnosis-the shift drum has a large chunk broken out of it (yes, I found the chunk). Pics to follow later, courtesy of sstewart. I was way too busy ripping into the heart of the beast and too greasy to photo-document the operation.
It was a relatively painless disassembly, with one anxious moment- no 46mm socket (or 1 13/16"). sstewart made a quick run to Tractor Supply for the save!
A intermittent clatter was also diagnosed as a malfunctioning cam chain tensioner.
Now all I have to do is shell out some quickly diminishing cash, wait a bit and reassemble!