[1 Wheel Drive]

Try taking it apart and cleaning things up. It is a compression sleeve with several vertical slits in it to form fingers. When the nut is tightened it compresses the fingers around the shaft of the mirror stem. If the slits between the fingers are filled with crud or corrosion it won't grip the shaft properly.

Or you could just replace the mirrors with the much sexier Aprilia Tuono mirrors. They are dirt cheap (paid < $25 each for them at the local Aprilia dealership) and look like this:

Note that I also have mirror spacers for higher/wider mirrors 'cause I'm a big lug.

 

[OydnaR]

My left mirror stem turns due to wind pressure when I ride. I tightened the bolts but the stem still swivels..
Any thoughts?

Thanks

if its still under warranty, take it back to dealer, I did, got a new mirror on the side that was drifting with wind pressure