Thanks Rob,
I did remove the aftermarket mirrors first! :-D
Well, I'm not really sure how these OEM mirrors are meant to be installed. The aftermarket mirrors have stems with threads on the ends, so they screw into the black handlebar switchgear modules. When you have them at the appropriate position on the last rotation, you can tighten the lock-nut to keep them there.
However, the OEM mirrors have stems that seem to end inside a projection of the lock-nut, because the visible threaded end looks like it is part of (moulded with) the lock-nut. Hence, even if I loosen the stems from the lock-nut, I have no idea how to tighten it in the appropriate position.
Hmm, good point - I didn't try turning them the other way. Let's try again, and yes I too am dreading putting a flame to them.
CheerS!