why is the cowling now catching?

All had to be removed to get at the keyway that had sheared. Now my old 3hp briggs and stratton starts at last but quickly follows with a terrible screeching. Tried everything and proved the flywheel is catching on the cowling by pulling the cowling off asap. What am I doing wrong? It fitted before. There is one washer slightly convex/concave.I fitted it between the pawl and the flywheel ,convex.
Maybe I had better try to arrange the starter without the pawl mechanism and somehow fixing a slip off rope start instead,leaving the cowling off. But how do I do that? I would rather keep the pawl and cowling though if I had a choice