OK it was the clutch cable, I needed a new one. I got a nylon one from Motion Pro and spent 2-1/2 hours swapping it in. It took me that long because (a) I'm a total newbie at this and (b) both the Clymer and the owner's manual have basically the same steps with the same pictures.
The Clymer book has this on removing the clutch cable (nothing on re-attaching one; I guess it's obvious that it's the same steps in reverse):
Originally Posted by Clymer
Disconnect clutch cable as follows:
a - At the cable center adjuster, loosen the cable adjuster locknut (A, Fig. 40) and turn the adjuster (B, Fig. 40) all the way in to allow maximum slack in the cable.
b - At the hand lever on the handlebar, loosen the cable adjuster locknut (A, Fig. 41) and turn the adjuster (B, Fig. 41) all the way in to allow maximum slack in the cable.
c - Align the slot in the cable adjuster locknut and the cable with the cable and release the cable from the adjuster and the hand lever.
The Owner's manual has the same pictures of where the clutch cable lock nuts and adjusters are at the lever and at the center, and no more information.
What I had to figure out on my own (which I assume is par for the course) was:
1 - How exactly the cable is meant to come out, particularly from the bottom connection where it attaches to the transmission. I could only get enough slack on that end if I detached the top part first. I figured that was why they gave that direction in (c) without mentioning the bottom part in a theoretical step (d).
2 - The fact that I had to remove several parts of my bike to be able to get the cable free. My VN750 has an engine guard on it, which I had to loosen and move out of the way; then I found out I also had to remove the gear shift foot lever in order to get the space to fiddle with and remove the clutch cable. All the bolts needed a different sized metric hex nut, too.
But now the clutch is silky smooth. The old cable was full of rusty looking gunk.
But shifting gears still operates with a "clunk" or "chunk". I'm gonna have to keep looking at what else to lubricate on my '94 bike. That, and try the Grambo trick for that intermittent ticking sound when idling.