The pull-cord spool on top of my 6HP B&S makes a loud metallic rattle while the engine is running. It sounds like there may be some interference with each rotation of the spinning cooling system, but nothing appears bent out of place. Slowly pulling the cord while the engine runs makes an especially loud screech, and sometimes this causes a momentary cessation of the rattling. Importantly, the rattling began when I bumped the front of the engine (not the spool or spinning part) into an obstacle. I removed the plastic cover to inspect for damage, but nothing appears wrong. Has anyone else experienced this? Any remedies?