Here is a quick paper on the MadDad Modification to the Intruder 1400's rear end.
We will do a better version, soon. I needed to get this up quick for Ron.

I have attached another small pic. of the brass fitting's birth.

1.   The left object is a 1/2" pipe to 3/8" OD copper tubing fitting. What's
nice about this part is the inside diameter of the hole is just the right size
for a 5/16' tap, course or fine. The Visor lights come with a 5/16" hollow bolt
for the wiring. It would be easy to drill out to a 5/16" hole needed for a 3/8"
bolt tap.

2.   The second picture has the small end cut off and tapped the brass piece to
5/16" NF.

3.   The third pic. is the fitting turned down to @ .62" which fits in the frame
hole on the bike. Now I don't have a metal lathe. I chucked a spare bolt with
the head cut off, and the brass piece threaded onto that, in a drill press then
with files, course then fine, "turned" it to size. It didn't take but about 10
min.

4.   I tried several options, and the forth object is one I rejected. It is the
right length @ .56" with a 6 mm tapped hole for the screw that holds it in
place. I tried turning  the piece to @ .55" in dia., and filing groves to hold
some O rings for shock absorption, but it was a pain to get everything the right
sizes. May try again this winter. I ended up turning a piece @ .56" long and of
a diameter, @ .58" that which combined with a single layer of thick
electrician's splicing tape for vibration absorption came out to .62", with a
spot cut out for the screw that holds it in place.

6. I screwed the hollow bolt onto the brass piece, then the light onto the bolt
that was sticking out. I then held this in place and marked where the 6 mm screw
would go onto the brass piece with a Sharpie. Drilled and tapped that hole in
the brass. Put it all back together with locktite and screwed it down. Did have
to grind off about 1/8" of the 6 mm screw as it was hitting the 5/16 in bolt and
not snugging down the brass piece.

7.   Again I had to take out the rubber grommet that is in the fender hole to
make enough depth to allow for the bolt head. I thought about cutting off the
bolt head and just using the hollow threaded part, along with some set screws,
but time was my first consideration. The wife wanted to go for a ride, not watch
me sweat in the garage.