A:Answer I use my mounts on my motorcycle helmets. There have been a few times where I've lost my replacement mounts and just didn't feel like leaving the house to buy another, in those cases, I use my heat gun (you can use a hair dryer) and slowly go over the mount, warming up the adhesive, and it comes right off. So to answer your question, removing the mounts with a heat gun or a hair dryer will remove it cleanly from your helmet w/o leaving anything behind. To be safe, wipe the area with alcohol after taking the mount off to clean off any leftover residue.
*Read at your own risk from this point forward*
Now, you're not supposed to "reuse" mounts once the adhesive's already been used, but I have before and I have yet to have any issues. I honestly have too many mounts as it is and I don't need any more. So I do take some off with my heat gun when I no longer use that helmet, and I reinstall it on a new helmet WHILE THE ADHESIVE IS WARM from the heat gun and after cleaning the helmet part with alcohol. This works for me, it may not work for you so try it at your own risk.
Hopes this helps.