It's important to use a degummed castor oil in model engines or they'll soon wind up covered in a thick sticky tar-like varnish that will rob them of performance and may even stop them from running.
That tar like varnish is not gum. Castor gum is in Bakers A not AA, it never was in AA so to say it is degummed is not accurate. If it was degummed then it is inferior oil.