Small Engines (Lawn Mowers, etc.): Lawn Tractor Leaking Fuel, leak fuel, cold weather

Question
I own a well maintained 2 year old 20hp v-twin Briggs Yard Man.  It has begun to leak fuel while in short-term storage (between uses).  It leaked aprox. 1/2 gallon into the oil and some onto the floor.  Could this problem be related to the cold weather? The tractor is stored in an unheated shed.  I have replaced the fuel filter, changed the plugs, changed to 5W 30sae. oil, and added stablizer to the fuel.  I plowed snow with it when done, is there any suggestions so this doesn't happen again?

Answer
It sounds like a small leak from the carb caused by either a bad needle and/or seat or, less commonly, a bad gasket or porous casting.  I recommend, because of the tractor's age, you contact an authorized dealer before you proceed on your own.  There may be a service bulletin or recall for this problem.  Hope this helps.