Could you help solve this lawnmower mystery?

So. Briggs & Stratton 300. Oil is good, gas is a bit debris-filled but that hasn’t troubled in the past. Spark plug is new. I shot the engine full of starter fluid.

I prime it, start it, pull the cord. The engine catches on the first or second try. It vibrates. There’s a loud, clattering/squealing sound. Then the engine stalls, and I wonder if maybe I shouldn’t just get a dang reel mower and be done with it.

Suggestions?