Rick

I think just vibration from the motor can do damage. I was riding to work every day on the road (a couple of years ago now) and noticed a crack in the steel. It gradually progressed until I got to work one day and the R indicator was hanging by it's wire. Luckily I had a wreck with a spare mount so I swapped them over. 
I was only only going to weld the mount itself, not the fender. The mount itself is fine but the holes are quite large as they are designed for the protruding part of the rubber mount that has a sleeve inside it but the rubber part is no longer attached.
I've decided to go to the rubber shop this arv to find something to make some rubber washers.

Ash
Thanks for the suggestion. I'm in Oz so not familiar with that shop. We do have a general rubber place so I'll see what they have. If I get some sheet I can cut out rings then use a wad punch (I have multiple sizes I use for making wads for black powder cartridge reloading) to cut holes the same size as the steel collar.

I'll take some photos of before and after and post them.

Justin