Hi!
The only thing that will loosen up old castor oil gum inside the engine is heat! Alcohol or acetone won't do!
Warm the engine ...either with a propane torch or heat the engine in the oven.
But! There is a but to this....The only thing that can't be fixed this way is the ballbearings!
They must be replaced by new ones if you are serious.
If you want to cheat...just let them be[:'(]


Regards!
Jan K