Heat it up to get it so you can get it to turn then immerse it in methanol or glow fuel. Every so often stick a prop on it and work the crank back and forth. The heat will loosen it up but once the sticky oil goo cools it will solidify and make things tough to turn over. The last gummed up carburetor I had to free up needed a soak in methanol to free up and stay free. Heat worked as long as the carb was warm, adding oil didn't help. Just my worthless opinion.