My rototiller screams when it's running and the start rope unwinds. We put a new start wheel on it and greased it but it still screams. It's a Sears 206CC 5 hp
Replace the starter clutch. It's the thing that screws on the end of the crankshaft in place of a conventional flywheel nut. You may be able to get away with lubricating the existing one, but they ALWAYS completely seize up eventually. Not expensive.