That was a very common problem on the PM6 and early MM models. Some folks have had success reattaching the cup, I have several that I have reinforced before they separated, or the starter pulley can be replaced. Problem is, the replacement pulleys are all plastic and if you don't change the starter pawls or flywheel as well, the narrow metal pawls on the original flywheel will tear up the plastic pulley in a hurry. McCulloch had some kits with a new starter pulley, pawls, springs, and the pins (rivets).
I have all of the parts on hand if you want to persue replacement parts.
Mark