This mower has an odd history, but appeared to be in good shape. It was given to me by a friend, who picked it up from the curb in his neighborhood (it's a nice neighborhood). I don't know if he found out why it was being tossed out. He just picked it up as a repair project to do with his son, and then found out I was looking for one, and offered it to me.
It's a Briggs & Stratton 6.5 Hp engine. Looks to be only a few years old and in good condition. Friend put in a new air filter, spark plug, and I think also changed the oil. I checked the oil and it looks cleaner and new-ish.
I've used it several times this year. It's been running great, starts right on the first pull. Suddenly at the end of my last session, the rpms dropped but it kept running. When I turned it off I could smell gas a bit. Next time it started fine, but is still running slow. I managed to finish the yard with it running slow.
I've check the air filter and spark plug. Both look clean. There was a little oil or gas residue at the bottom of the air filter. There was a little oil on the threads of the spark plug screw, but the sparky end was clean.
I'm just trying to see if there's anything else I can do or check before getting into the carburetor.