Any tips or suggestions on working on oil lamps ? Chimneys on one side-lamp and the tail lamp of my '13 are quite loose.

Is it the cap or the total assembly? If it's the cap you can solder them using flux to draw the solder in. If it's the assembly, to do it right you will have to disassemble the lamp to remove the reflector, then you will see the flange that holds the chimney to the lamp. You can try to re crimp the flange or paint flux around the flange and solder it. I use a micro torch to do it but before that I used a propane torch. Don't forget to position the assembly so the name is facing the correct way, don't ask how I know this. If you are less interested in the total look you can try and flux and solder from the outside but you will have solder showing unless you paint over it

Apparently the paint that I used on the cowl lamps on my '21 Touring was not hi-heat. The paint has blistered.

John, thanks for the reply. They are John Brown, seems only the top brass cap is loose.

I had a loose one once, eventually it vibrated off! They are crimped.