If there are no plastic parts in the bell, try acetone first (dissolves cyanoacrylate superglue and some other glues without harming much else), then try solvents for plastic (be VERY careful with these if there's anything plastic or silicon in the endbell that you can't take out). Lots of adhesives are thickened with some type of plastic, so if you break that down, the rest of the glue will break more easily.
I recommend superglue to reattach the motor. If there's a flat polished piece to place the magnet, use normal superglue. If the area or the magnet is rougher or doesn't fit perfectly flat, use gap-filling.