Small Engines (Lawn Mowers, etc.): riding tractor lawn mower - fuel in oil, blown head gasket, carburetor body

Question
This has happened several times now.  I try to start the mower, the engine makes maybe a 1/2 revolution.  I try again.  By the third time, if it starts, I get white smoke from the front grill with an oil spray.  I get a strong smell of gas.  I shut down the engine.  The oil dipstick is on a very high level and smells of gasoline.  I drain the oil which ends up being all the oil with twice as much gasoline.  I also of course replace the oil filter.  If the engine fires up the first time I try, no problem.  Someone suggested a stuck float.  I took off the carburetor.  The float seems fine.  There is a solenoid on the bottom of the carburetor bowl - fuel shut off, I assume.  What do I do next?  Briggs & Stratton model 31G777, type 0165E1, code 021026ZA, 17.5 HP

Answer
Hello Dan:

The Solenoid is an Anti Diesel Solenoid. If Shuts Off the Gas to the Main Jet and is Supposed to Help Prevent the Backfire Many of the Engines Without this Solenoid Make when the Engine is Shut Off. The Carburetor Needle Valve is Not Seating Correctly. Usually the Gas in the Crankcase Oil or White Smoke is Caused by the Carburetor Float Needle Valve is Not Seating Properly and Allowing the Gas to Flood the Carburetor and Engine. Then the Gas Seeps by the Rings and Enters the Crankcase and Contaminates the Crankcase Oil, a Bad Diaphragm in the Fuel Pump, a Blown Head Gasket between the Cylinder and Push Tube Galley, the Crankcase Vent Stuck/Frozen/Broken or the Carburetor Flooding the Engine. 1- Clean the Carburetor and Replace the Float Needle Valve (and Seat if this Model has One). A-  **Remove, Disassemble and Soak the Carburetor Overnight in Carburetor Cleaner (I Use Gunk). I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning. You Only have to Remove the Bowl (if Applicable), Float Pin (if Applicable), Float (if Applicable)  and Needle Valve and Any Adjustment Screws that Go Into the Carburetor Body. The Welch Plugs Do Not have to be Removed. Then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts. Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidental Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required.** If the Carburetor Float Needle is Good, then; 2- Block the Outlet Port and Pull a Vacuum on the Fuel Pump. If it Holds Vacuum, then it is Good. If Not, then the Diaphragm is Busted and the Pump Requires Replacing.  If the Fuel Pump is Good, then Check the Crankcase Oil for Gas Contamination. If the Crankcase Oil is Contaminated, then Drain and Refill the Crankcase Oil with Fresh Oil. 3- **If the Mower has a Manual Gas Shut Off Valve:  Check the Manual Cut Off Valve and Make Sure it is Cutting Off the Gas Flow to the Carburetor. A- If Not Stopping the Gas Flow, then Replace the Valve. A- If the Mower Does Not have a Manual Cut Off Valve: Install a Manual Cut Off Valve and Turn Off the Gas Flow when the Engine is Not in Use.** 4- If the Valve is Good or has Been Installed, then Remove the Cylinder Head. On the OHV Engines the Head gasket will Blow Between the Cylinder and the Push Tube Galley. This Allow Oil to be Sucked Into the Cylinder from the Crankcase and the Extra Oil is Just Enough to Cause the White Smoke. 5- Check the Crankcase Breather and Make Sure it is Clean and Operating Properly. If the Crankcase Breather Sticks, then Oil is Pulled from the Crankcase into the Carburetor Throat and this Causes the White Smoke.  You can View a Breakdown/IPL of the Unit at this Site Addy; http://www.briggsandstratton.com/maint_repair/manual_and_more/doclist.aspx?categ... and Enter the Model Numbers (XXXXXX) and Type Numbers (XXXX) in the Appropriate Boxes and Click GO. Then Select Download PDF. 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

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Respectfully

John