I have a 18.5 HP Briggs and Stratton engine and the exhaust valve seat came loose. What would cause that to happen? Model 31P777-0348-E1. I also cannot find the seats listed in the B&S parts list. I guess you have to buy the head. Have you heard of this happening before?
Normally due to overheading of the head. Grass buildup or from leaked oil and dirt sticking to it. See one every once and a while. When the head gets too hot the aluminum expands and the seat loosens and out it comes.
