Well... that could have been worse...

[Wrecent_Wryder]

34

[sledge]

My speedo/tacho cables were always coming loose at the collars. I was a bit reluctant to use Locktite in case I couldnt undo them If I had to without damaging the threaded section that the cable collar fixes over. I was also careful about overtightening them for the same reason. I used a few turns of PTFE tape on the threads and tightened the collars by hand......they have not loosened off since.

[Wrecent_Wryder]

43

[sledge]

I dont doubt Blue loctite would be ok on any other threaded fastener but the threads on the back of the gauges are very fine and they dont look like they have a lot of strength in them, my concern is that you may shear the whole threaded section off the back of the gauge if trying to undo the collar with Loctite on it, particularly if you use pliers and loose the "feel".

[Mandres]

One trick that I've found works pretty well is to apply a couple drops of the Blue Loctite to the screw, thread it in, wait a minute or two and then remove the screw again and let it dry fully.  The sealant won't actually bond the fastener to the hole but it will create enough of an interference fit to keep it from backing out.

-M

[Blueknyt]

dab of RTV sealer on collar once its tight (like the purple/yellow factory settings tattle tail paint) wont vibrate off, and you can scrape it off easy enough.

[runsilent]

Tighten them with a pair of pliers and they will hold forever.  Just snug them a bit past finger tight.  Works for me.  Will hold till you loosen them.

[Wrecent_Wryder]

4d

[RedShift]

... As I posted elsewhere, my gauges were loose in their housings. With the cap nuts on the back tightened all the way, they were still loose- the gasket around the rim didn't even make contact. I think the vibration was contributing to the cables loosening. I put rubber washers between the steel washers and rubber grommets underneath the four cap screws, and all of that is snug now.

This is a common condition.  The Cap Nuts can only pull up on a small amount of bold before it bottoms out.  Your solution of more washers is the right answer, one I should check on as well.