Small Engines (Lawn Mowers, etc.): craftsman mower oil leaking etc., excess fuel, craftsman mower 917

Question
Hi, trying to get a craftsman mower 917.376572 working. When running, a steady stream of oil (black) drips out of the muffler. RPMs are very low. Removing the muffler, I don't notice any oil spitting out of the engine, seems to run ok. Also, notice a little oil (clear) in the air filter. Wondering if replace the muffler will help?

Answer
Looking at the engine on the Briggs site, I would say that the muffler is fine.  More likely, the engine oil level is "over-full",
or the mower was tipped on it's side.

  How the oil level could get over filled, the carb could be flooding and the excess fuel is getting into the engine, thus adding
to the oil level, and making it over full.
If so, the dipstick would smell like gasoline, so check that.
If tipped on its side, and if oil is up near the air filter, if it is
paper, it needs to be replaced, but wait until you figure out what is wrong.

I would suggest draining all of the gas and oil out, and starting fresh, putting in new oil and gas, and starting the mower without the
air filter, and let it run a bit.