I think I finally fixed the damn filler bolt. The first time around I used a Permatex epoxy thread repair kit, which seemed to work at first, but the bolt was loose the following morning.
There's a gap between the threads and the flange of the bolt. It occurred to me that the metal washer that fits under the flange might not have been thick enough to keep the bolt from going in too far past threads and working itself loose. So I got a neoprene washer and cut the center wider to fit over the threads. It grabbed better but was still stripped.
This morning I degreased and cleaned the mating surfaces again, applied a lot more of the permatex, and inserted the bolt using the two washers. It seems to have worked this time. I showed my bike at a vintage rally this morning, and there was no oil puddle underneath it when I left. Nothing new on the garage floor, either, since I've been back. Bolt is still on tight. Fingers crossed.
Now on to that exhaust leak...
Jeff