Oh, the joys of riding an old motorcycle that had lived under a tree for 15 years and was partly disassembled. When I started riding the Dawg I knew that the sight plug hole had been stripped and what looked to be a 1/8" NPT brass plug had been installed. It looked/felt secure so I didn't screw around with it. Yesterday I happened to look down at the final when I had the R/H saddlebag off and noticed "no plug"!! I guess I can blame it on Bob.

The hole was already huge and I didn't have a plug big enough so I drilled the hole a bit larger, tapped it M12x1.5, and decided to make some sort of insert.
I coated the drill bit and tap with sticky grease to catch the chips and then prepared the hole:

I then turned down and tapped a short piece of aluminum to M12x1.5:

Then drilled it through with a 5mm hole and tapped it to M6x1.0:



I then parted off the threaded piece I was going to use for the repair. I inserted a 6mm bolt with lock-nut, coated the insert threads with JB-Weld, and then screwed it into the freshly tapped and cleaned hole. I flushed both the insert and tapped hole with lacquer thinner before gluing it in.
The insert was first screwed in with low torque:

Then the bolt and jamb nut were removed after the JB-Weld had set up:

I then made a new plug from a 6mm stainless steel bolt and fitted a copper washer:

The new plug was then installed into the repaired hole:
