Before you go any futher with that motor, block/plug up openings leading inside. Like case vent, stator area, intake and exhaust. Get enough kerosene to fill a sprayer bottle (about a quart) and spray that thing down. Let soak for a day or two whilst misting periodically to keep moist or wet. After that get some L.a.'s Awsome Cleaner from dollar store and spray on full strength and let sit fow a few hours. Re apply periodically to keep wet then rinse with hot water and long bristle brush. There may be a few stubborn spots that need a second application.
The kerosene will break down grease, oil and chain lube. The Awsome Cleaner will remove all of it after the kerosene has done its job. (edited)