I just removed the reflectors from my denim black street bob (rear fender) last week.
I did the following and it worked like a charm:
1) Spray a (little) bit of wd40 on the foam area behind the reflector and let it sit for about 5 min (make sure it does not drip on your brake pads or belt, just in case)
2) Get a hot air gun that you can set to a certain temperature, about 50-79 degrees Celsuis is okay. Heat up the reflector area evenly, but make sure you don't overheat the parts.
3) Pull the reflector off, this will go easy when the temp is high enough.
4) remove the chunks of adhesive with your fingers (after heating up the part where they were sticking on the bike with your hot air gun)
5) shine up your surface with some pledge and a dry cloth.
Done!