We may have a few problems there Stuart. I think the first thing you need to do is to remove the engine from the mower, and see if it is still stiff. If the problem is just an alignment one, the engine may be free to rotate once it is removed from the mower. If it is still tight, it is going to be necessary to remove the crankcase cover again and reassemble the engine step by step. Please do not try to start the engine until we get this resolved.
