Normally they are held on with three synco mount clips, often with allen head screws, that fit in a circle milled around the mounting end of the resolver?
What make of motor, if you can post a picture it may help.
IOW most of the time you can remove from the Body end of the resolver, otherwise it would entail getting access to the shaft end, they are often coupled to the driving element, by a small flexible coupling that has to be released before removal.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.