Questionhi john-its ed with the 17.5hp model 31c7070154e1 that backfires after i replaced the alternator on the riding mower. When i tightened down the fly wheel the first time i used a 12 inch crescent and pipe wrench. So I took your advice and unloosened the fly wheel to check the key. I had to use a hammer to pound the crescent wrench to unloosen the nut for the fly wheel. So it might have been more than 100ft lbs. The manual said the gap was between .010 and .014. I tried them all. Next I gapped them from .010 to .025. It didn't backfire at all at .025 and at .024. But the rest on down it did. I took the carb apart and checked the float needle and carb for obstruction. Also checked the antibackfire solenoid and it tested good. I checked the spark at the plug by pulling it from the engine to make sure the spark was consistent. Do you still feel its the key. If so I will replace it. May the Lord bless you for helping me. Thank you.
AnswerHello Again Ed:
>>Thanks for the Kind Words. You and Everyone that I Assist is More than Welcome to "Pick my Brain" so to Speak and I Hope I am Helping People Save Time and Money with the Answers I Provide.
>>Thank you for Using All Experts.
>>From your Description it Sounds like the Flywheel Key is Damaged.
>>Setting the Coil Farther Away from the Flywheel Changes the Firing of the Coil Slightly as you have Seen yourself.
>>Are you Sure the Valve Clearance are Correct? .005in Intake and .007in Exhaust
>>The Following is a Basic File I made for Setting the Valve Clearances. Any Input is Appreciated.
>>**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).
>>Check the Push Tubes and make Sure they are Not Bent.
>>Set the Cylinder you are Setting the Valves on to Top Dead Center on the Compression Stroke When Setting the Valve Clearance. Now Loosen the Valve Adjuster Lock and Using a Blade Style Feeler Gauge, Set the Intake Valve Clearance to .004in -.006in (Briggs Engines) and the Exhaust to .006in - .008in. (Briggs Engines) Loosen and Tighten the Rocker Arm and the Feeler Gauge is Placed Between the Rocker Arm and the Valve Top where the Rocker Arm Pushes on the Valve.
>>***BE SURE TO TIGHTEN THE ADJUSTER LOCK AFTER YOU HAVE THE PROPER VALVE CLEARANCE***
>>I have had Better Performance Out of the Mowers and Less Burnt Valves Using these Settings. Be Sure the Piston is at TDC on the Compression Stroke.**
>>If you Remove the Valve Cover and then Turn the Engine by Hand, you can Watch the Intake Valve Movement. When the Intake Valve Closes, the Piston will Just Starting the Compression/Power Stroke.
>>On Some Engines you can Us a Straightened Coat Hanger and Feel the Piston.
>>Be Careful and Don't Jam the Wire in the Cylinder. Usually the Piston will Push the Wire Out of the Spark Plug Hole with No Problems.
>>I Usually Set the Coil at .015in or .020in from the Flywheel Depending on How the Engine Runs at .015in.
>>The Following is an Instruction File I Made to Replace the Ign Coil. **Using the Provided Site Addy, Locate the Breakdown for the Engine to Assist you in Doing this Repair if you Require it.**
>>Remove the Ign Module/Coil Lead from the Spark Plug.
>>Remove the Blower Housing (metal engine cover). Under this you will See the Ign Coil (has the Lead to the Plug Attached to it. Unbolt the Ign Coil and Remove the Coil.
>>Use a Section of a Soft Drink Carton (example: a Mt Dew 24 pk Side Panel Cut to 3" x 6".
>>Turn the Flywheel so the Magnet is Facing the Ign Coil and Place the Cardboard Section Between the Ign Coil and the Magnet.
>>Let the Magnet Pull the Ign Coil to the Flywheel and then Tighten the Ign Coil Mounting Bolts.
>>Turn the Flywheel and Pull the Cardboard Panel at the Same Time and Remove the Panel from between the Flywheel and the Ign Coil. Connect the Lead/s to the Ign Coil.
>>Replace the Blower Housing and Any Other Hardware you Removed to Remove the Blower Housing.
>>Attach the Plug Lead to the Spark Plug.
>>Now Start the Engine.
>>Check the Valve Clearances before you Remove the Flywheel to Check the Key and Set the Coil as I have in the Instruction File.
>>Did you Mount the Coil with the Stamped "This Side Up" Showing?
>>You can View a Breakdown/IPL of this 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.
>>As Always, If you Hit a Snag or this Does Not Correct the Problem, I Hope to be Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Happy. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 5 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. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
