I have the same problem. Replacing the "flame arrester" (it's not a
muffler) didn't help.

wrote:
Anyone have any ideas how to quiet my riding mower with a 10 hp
Tecumseh engine,It looks like a cheap muffler for what I know about
mufflers,I replaced it with the same model muffler,no change in the
noise,which told me my old muffler was ok,does anyone have any ideas
how I can quiet it.10hp murray riding mower with a Tecumseh engine.12yr
old mower,runs great otherwise.