Loose Bar End Mirror

The first thing I would do is unscrew the mirror head from the top of the stalk using an 8mm open ended spanner to have a closer look. It looks like the ball joint has probably been installed from the inside before the glass was fitted so unless the glass can be prised out without breaking it there may be no way of fixing it? I have no issues with my 2019 Speed Triple mirrors. The only option might be a new mirror unless anyone else has any ideas.

 

A number of Speed and Street Triples are prone to this especially at higher speeds, it is difficult removing the glass to access the rear without the glass cracking, I have sorted a couple for people now, what I did was mix a very small amount of black epoxy resin, then carefully placed this around the ball joint, I did this using very small artist brushes, cheap to buy as they are useless afterwards, you can't tell once done, the only issue is that you can't adjust it afterwards, however if it's only you riding it and it is set right for you, then there is no problem, it certainly doesn't move afterwards.

 

Assuming it is only one mirror affected, I would also swap them over so that the more important right side mirror is still adjustable with the other side glued.