B+S Mower smoking after use

[Beets187]

I bought a used MTD push mower last year with a B+S engine. Not sure of the age and specs but I can get them if it makes a difference.

The mower runs well but just sounds "off". Maybe an engine knock or something but I'm not overly sure. My main concern though is that every time I'm done cutting my lawn, I can smell something burning and I can see small amounts of smoke coming out of the top of the engine. If I open the gas cap, the tank is also filled with the same smoke.

I have since replaced the oil, air filter and spark plug. No changes noted.

Thanks for any suggestions

 

[Hammermechanicman]

Have you pulled the shroud to see if fluffy built a nest in it?