Small Engines (Lawn Mowers, etc.): Engine backfires plus, briggs and stratton, crank case

Question

Hi John,

 The model # is 286707, Type 0114-01, Code 91012531. My other lawnmower here had the  same carburetor. I changed the carburetor over to the other one.  Still backfires and still runs very roughly.  Is there any timing for the governor on this model. could the backfiring part of it be ignition related. or would it be something wrong with some other part of the engine. I checked the flywheel key.  It is okay!thanks for your time.

Followup To

Question -
a recently purchased a lawn chief lawn tractor. the engine always backfired when going from fast throttle to slow.  The engine also had a leek down on the PTO side. I took the engine apart replace the seal.  Also had to replace the crank case seal. put everything back together.  Runs okay under load with the blades turning.  Also idles okay.  But when no load placed on engine in fast speed.  Engine runs roughly.  You can see the governor going back and forth.just wondering if there's any type of adjustment to correct this or is there some type of timing for the governor.I have see L head service manual but don't see any information about that.  Nothing else moved in the engine.  Only the governor/oil slinger the engine is a Briggs and Stratton model number 286707. it is a 12.5 hp motor.  Any help would be greatly appreciated. Thanks

Answer -
 Hello Jeffery:

 For Briggs Engines I need the Type and Code Numbers Also in Order to Get a Diagram of the Engine. However, If this Carburator has a Screw in the Bowl with a Spring Around it. Turn this Screw In(clockwise) 1/4 Turn Untill the Engine Smooths Out. Make Sure the Engine is on Full Throttle when Adjusting this Screw and Be Sure to Stop as Soon as the Engine Runs Smoothly on Full Throttle. If this Does Not Help, then the Carburator need to be Cleaned and Rebuild. Hope this Helps. Let me know what Happens.

 Good Luck

 Respectfully

 John

Answer
 Hello Jeffery:

 You can View the Engine Breakdown at this Addy http://shop.briggsandstratton.com/BShopProductListingPage.asp?MecID=100&CatalogI. If you are Sure the Carburator is Working Properly and you Removed the Flywheel to Check the Key, then Check for a Burnt Valve or Improper Valve Lash(clearance between the Valve Steem and the Tappet). From what you Described, Did you have the Governor Control Arm Loosened or Take it Off the Governor Shaft? If so let me know and I will explain How to Set the Governor. Hope this Helps. Let me know what Happens, Please.  

 Good Luck

 Respectfully

 John