Small Engines (Lawn Mowers, etc.): Smoking Briggs and Stratton, briggs and stratton, breather vent

Question
I have a 31C707 - 0230-E1 B&S engine on my mower.  It was running fine the suddenly stopped.  I noticed some leakage of gas and have replaced the seal, pin in the bowl float.  When checking the around the rocker cover I felt a mixture of oil and gas.  I changed the oil, filter etc.  It starts and runs great for about 15 seconds then profusely belches out grey smoke.  Any incisive thoughts?  

Answer
Hello Tom:

Sorry for the Delay. This Question was in the Question Pool. Clean or Replace the Crankcase Breather/Vent. When the Oil and Gas Mixed it Overfilled the Crankcase and Filled up the Crankcase Breather/Vent. Now the Breather/Vent is Stuck Open and Oil is Being Sucked Into the Carburetor. I Suggest you Install a Manual Cut Off Valve in the Gas Line. The Problem will Return in about 1 Season. There is a Problem with the Needle and Seats in the Carburetor and they Tend to Leak Gas By and Flood the Engine Crankcase. All the OEMs are having this Problem. You can View a Breakdown/IPL of the Engine at this Site Addy, http://www.outdoordistributors.com/ and Select the B. Then Select Briggs and Stratton. Then Select Don't have Part Numbers. Then Select the File #31. Then Select the Folder #31C700. Hope this Helps. I am Here if You Require More Assistance. Let Me Know What Happens, Please. Thanks.

Good Luck

Respectfully  

John