Small Engines (Lawn Mowers, etc.): Craftsman Riding Mower - Gas getting in oil, crankcase oil, carbureator

Question
5/27/2008
Model # 917273640 - 18.5 hp
I am having problems with the gas getting in the oil in my craftsman riding mower - I was told it was the carburetor, so I purchased and replaced the carbureator, but am still having the same problem - If I change the oil, the mower will run about 10 minutes then when the gas mixes with the oil again, the mower stops and will not restart - any help you can give would be greatly appreciated.
Thanks,
B Dorsey

Answer
Hello Barry:

Usually the Carburetor Needle Valve is the Cause for this Problem if there is No Vacuum Operated Fuel Pump on the Mower/Engine. To View a Breakdown of this Unit Go to this Site Addy, http://www.searspartsdirect.com/partsdirect/index.action and Enter the Model Numbers and Click Search. From this Page you can View Diagrams and Parts Lists for you Equipment Using the "View Sub Components" Section. You can View a Breakdown/IPL of the Engine at this Site Addy; http://www.briggsandstratton.com/maint_repair/manual_and_more/doclist.aspx?categ... and Enter the Model Numbers (31p777) and Type Numbers (0348) in the Appropriate Boxes and Click GO. Then Select Download PDF. According to the Breakdown for this Engine, there is a Vacuum Operated Fuel Pump. Since you Eliminated the Carburetor Needle Valve by Purchasing a New Carburetor, then the Diaphragm of the Fuel Pump is Split/Cracked and is Leaking Gas Into the Crankcase Oil. The Fuel Pump is Shown on Page 4 of 12 (on the Briggs Site) and is Breakdown #387. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.

Respectfully

John