ORIGINAL: WALKERS210-RCU
Learned from and older gentleman, take the engine apart as much as you can without breaking bolts-screws. Put engine in a pan of water with Dawn Dish liquid, just a few drops, bring to boil. Unbelievable how it will loosen all the parts and clean it up. Don't leave it boiling cause you will have bubbles all over the stove which makes MAMA very unhappy.
I learned here some time ago where some guys swear by a product called Dawn Power Dissolver.
Bill