Small Engines (Lawn Mowers, etc.): Riding Mower Engine backfire, twin cylinder engines, briggs stratton engine

Question
14.5HP Briggs & Stratton engine (Model 287707)on 42" cut Murray rider.  Engine begins to sputter after about 30 minutes run time.  Ocassional backfire with real fire out of muffler.  What's happening and what do I need to have fixed?

Answer
Hello Ron:

Check the Gas Tank Cap and Ensure it is Venting the Tank. The Fuel Shut Off Solenoid in the Carburetor Bowl can be Heating Up, the Valve Clearance May Require Adjusting and the Coil/Ign Module/Magneto May be Getting Hot and Breaking Down. All of these are Time Sensitive (15 to 30 minutes Running Time) and can Cause this Problem. If the Plug Seems to be Firing Properly, and the Gas Cap is Good,  Check the Valve Clearance and then the Fuel Shut Off Solenoid. To Check the Valve Clearance; I Do Not Use the Setting Called for by the OEMs. I have Found that the Following Works Best. Remove the Valve Cover (on the Dead Cylinder for Twin Cylinder Engines). Set the Cylinder you are Setting the Valves on to Top Dead Center (Both Rocker Arms will have Play in them when the Engine is at TDC) When Setting the Valve Clearance. Now Loosen the Valve Adjuster Locks and Set the Intake Valve Clearance to .003in -.005in and the Exhaust to .008in - .010in. I have had Better Performance Out of the Mowers and Less Burnt Valves Using these Settings. To Check the Fuel Shut Off Solenoid; Remove the Carburetor Solenoid and Go to the Hardware Store. Purchase a Bolt of the Same Diameter and Threads. It Needs to be 3/4" Long. Put this Bolt in Place of the Solenoid. If this Corrects the Engine Problem, then Replace the Solenoid. ***NOTE: THIS IS FOR CHECKING THE SOLENOID ONLY I NEVER SUGGEST YOU OPERATE THE ENGINE WITH THE SOLENOID OUT OF THE CARBURETOR EXCEPT FOR TESTING PURPOSES*** Sometimes the Plunger is Moving, Just Not Far Enough to Allow the Gas to Enter the Jets. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. 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 9pm EST (US). My New Day Starts then. Thanks.

Respectfully

John