I was one of the ones that didn't have problems ..... until now. One... the stem on my right side one won't stay tight. 2..... the right side mirror itself keeps spinning loose.
possible causes: poor or stripped threads on the parts--over-zealous chroming of the threads.
I had that happen while installing my "old-guy" Magna's. If it's the right side you've got a thread or human issue; as in people keep bumping into that rt-side mirror. That side is the least likely side to become weakend since it should tighten each time something bumps or hits it.
Remove everything on that side: mirror from stem, stem, adapter and take a small flashlight and really give those threads a once-over.
If necessary, order another set of adapter bolts. In extreme cases: a new stem will be called for.
Now, let's re-install this sucker!
TOOLS needed: (your tool sizes may vary depending on adapter type)
5/16, 3/8 and 1/2" open-end wrenches
red Loctite (read the instructions. this is the really tough version of Loctite)
wire brush
goof-off (or similar oil removing product)
1. clean all threads with goof-off, inside and out with a small wire brush (or qu-tip for the inner threads) and carefully scrape off any chrome on the threads.
2. make sure the goof-off has evaporated thoroughly (that would be about 3 long gulps of lemonade for me)
3. put a drop or two of red Loctite on the SAE end of the adapter bolt and gently thread it into the stem. Once the adapter is threaded completely into the stem tighten the crap out of it with the 3/8" wrench.
4. Now, thread that locking nut onto the metric end, loosely, all the way up to the squared adapter bolt. (make sure the top end of this nut faces up)
5. gently thread the metric end of the adapter bolt into the OEM bracket hole. DO NOT USE LOCTITE HERE. If you ever want to replace that mirror, keep that hole clean. <chuckle> DO NOT TIGHTEN the metric end yet!
5. Put one drop of red loctite on the mirror bolt. (you said it was spinning, right? if yes, use the loctite--if no, do not use the loctite)
6. gently thread the mirror into the stem and tighten with the 5/16" wrench. Hold the stem while tightening.
7. Grab the stem and carefully turn and adjust it's position to suit your driving needs. If it screws all the way into the OEM bracket, that's fine. More than likely, it won't. You can tighten the stem at this point with the 1/2" wrench. Be prepard to retighten after step#8.
8. While holding the mirror in one hand and the stem in the other, adjust the mirror COUNTER CLOCKWISE or up and down until it reflects the area you want to see.
Do not spin it clockwise or you'll just be loosening it.
9. Once you've adjusted the stem and mirror to suit your needs take the 1/2" wrench and, if necessary,
re-tighten the nut downward (towards the OEM bracket) until it's tight.
10. the Loctite will need about 24 hours to cure--so, don't go out puddle jumping for a while.
If this doesn't fix your problem you're gonna need a complete new mirror set for the right side.
Sorry this is such a long post. Hope it has helped someone.