I do not know which side you are working on, but this should help , photos are worth many words.
GL1800 oem heated grips.pdf (application/pdf Object)
This will show you what you are dealing with and how things look.
They are glued on.
I have never removed a set that is good, so it will take more care and time and being careful
Usually I use an old screwdriver that I have rounded the tip off of, with a slight bend in it but to save good ones, hum?
I would use something flexible like a foot long by 1/4 inch metal strip with all the edges rounded off and smoothed well.
Start at the end of the grip after you take the end caps off, and work it around carefully and spray soapy water up in there all the time, use lots of it. Keep working it around and around, take your time, keep spraying the soap up in there, and it will just pull off when you get the glue bond broken.
Will it survive, ? Maybe.........if you are careful enough. On the throttle side might be best to just buy a new throttle sleeve, split the control housing and unloop the throttle cables and install a new throttle sleeve, ..........or just do not twist and pull much ,or you will break it.