You can use brake cleaner or carb cleaner, w/e. Engine degreaser will also work. Anything for removing oil/grease will help in this. Will take time so do it carefully if by hand. Engine Degreaser you spray on, let sit, and spray off with hose or bucket of water.
- Aaron
When I had to clean the motors after servicing them at the shop I just sprayed them down with Brake Clean and then dried it off with an air nozzle attached to the air hose.