Small Engines (Lawn Mowers, etc.): Briggs 18.5 hp ohv engine, craftsman lawn tractor, cylinder bore

Question
I have a Craftsman lawn tractor with the mowing deck removed and a plow attachment used for moving snow.  Several nights ago, my Wife ran it for an extended length of time with the choke left on.  I fired it up today and it runs well for a short period and then starts belching blue smoke out of the muffler and shuts down.  Afterwards, there is an oily run-off out of the bottom of the muffler that ends up on the garage floor.

Any ideas?

Answer
Dear  Joe,

An engine belching [blue] smoke possibly indicates >the fuel mixture is running rich.  Check if the carburetor is set properly. I'd check if the air filter is plugged? If so, clean and/or replace it.
Since the engine is belching smoke thats Blue. If this blue smoke is smelling like oil, it could be a problem with a) the rings b) the piston or cylinder bore, or all three. If the engine's knocking noisily, it's probably ready to be  overhauled.

Hope I've been of help for your problem.