Modern Vespa

My left hand mirror is ridiculously loose, it swings back and forth when I'm riding.. starting to get on my nerves

How do I tighten it? Do i need any tools?

This happens to me a couple times a year.

You need to get the right sized wrench and you have to carry it with you.

Also you may want to add a rubber washer? So it can be tighter?

I guess that is the thoughts behind it.

I'm sure many, many male riders will take me to task over this lame description.

But that is what I do.

Hi
Be careful tho mine came loose (the left one) i over tightened it and the thread snapped off,
I tried all sorts put in heli coil (new thread) came loose and even put a Riv Nut in and it gave up two weeks ago splitting the whole housing the thread sits in
Just brought a new brake lever with housing and its ok now with no movement

There will be a nut on the mirror stem. Screw it all the way up using your fingers. Then screw the stem clockwise until it gently bottoms out. Then turn counterclockwise to where you want it. Then turn the nut clockwise and tighten it down. As others have said don't over do it.

You might try a little bit of standard loctite on the threads before you tighten if they have a tendency to come loose. As the name says...it will lock things in place so vibration won't loosen them...and will be a LITTLE hard to undo if you ever want to re-adjust...but not TOO hard.
Good luck.

Yep, I often loosen the mirrors to get through narrow gaps. I don't think tools are necessary (at least I don't use them). Just get your fingers on that nut hold it steady and twist the mirror to tighten. You may need to experiment slightly to get the mirror in just the right spot but once you get the hang of it, it's pretty straightforward. Remember if you don't hold the nut with your fingers it tends to rotate with the mirror so can be frustrating otherwise!

^^^^ exactly what Matt says

17mm spanner to nip it up once in your desired position.