Depending on what glue you used a couple of things to try. A long thin screw driver can sometimes be worked in between the bar and grip (parallel to the bar after removing the end cap) and by rotating the screw driver you can work your way around to loosen the grip. Or try a little WD-40 squirted in between bar and grip using the plastic tube. Sometimes the grip will just pull off with a little twisting, again depends on what glue you used.