You could try spraying some penetrating oil on the crank shaft at the flywheel. Then put the engine on the side of a table with the crank facing upward and the edge of the flywheel on the table. Heat the flywheel with a heatgun. Then tap on the crank shaft with a hammer, but put something in between the crankshaft and hammer like a piece of wood, so you don't damage the crankshaft when you tap on it. Tap just a couple times, then rotate the flywheel and work your way around it.