Small Engines (Lawn Mowers, etc.): Briggs and Stratton 5 H.P. 130292 model possible carburetor issue, briggs and stratton, internal passages

Question
John,
Troy-Bilt Pony tiller with 5 H.P. B&S engine. Sounds like it is missing / sputtering under no load. New spark plug, new air filter. Old spark plug showed blackish soot(like too rich of fuel mixture.) Turned mixture screw in, did not seem to make any difference. Turned mixture screw out did not seem to make any difference. Seems to run good and smooth when tilling under full load. Runs rough with no load (not tilling) Does this sound like the carburetor needs cleaning? Full carb rebuild?  What would the symptoms be if the head gasket was cracked or broken. Thanks for your time.

Answer
Hello Jim:

The Carburetor, Valve Clearance or a Damaged Flywheel Key can Cause the Problem you Described. If you Turned the Air Mixture Screw and it Did Not Affect the Engine Operation, then I Suggest you First Soak and Clean the Carburetor. 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 # 13. Then Select the Folder # 130200. 1- The Following is a General Instruction File for Carburetor Cleaning.  Even though the Carburetor Looks Clean, the Internal Passages May be Restricted with Varnish that Gas Causes to Build Up over Time. I Suggest you Make Sure the Gas is Free Flowing to the Carburetor Inlet Port. If the Gas is Free Flowing to the Inlet Port, then  **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.*** (Do Not Use High Pressure Air for the Zama Carburetors, they have Check Valves for the Primer and these are Usually Blown Out of the Carburetor if Not Careful. Allow the Zama Carburetor to Set on a Drip Pan and Dry)***. Install New Parts if Required.** If Cleaning the Carburetor does Not Correct the Problem, then the Flywheel Key is the Next Step in the Diagnostics. 2- The Following is a General Instruction File for Checking the Flywheel Key. The Following is the Instruction File I Made for Correcting this Problem. It is the Basics and if you have a Question, Please Ask. ***Remove the Blower Housing (metal engine cover). Remove the Flywheel Nut or Starter Cup (Depends on the Model). Now Attach a Steering Wheel Puller to the Flywheel Using the Threaded Holes in the Flywheel. Tighten the Puller. Now Hit the Puller with a Hammer. Repeat this Procedure Until the Flywheel Pops Up or can be Lifted Off the Crankshaft. On Some Models you Can Not Use a Puller and Must Use a Pry Bar and a Pipe Cap that is Slightly Larger than the Crankshaft. Place the Pipe Cap Over the Crankshaft to Protect it. Place the Pry Bar Under the Thick Section of the Flywheel and Pull Up Against the Flywheel. **BE CAREFUL  DO NOT PUT A HOLE IN THE BLOCK UNDER THE FLYWHEEL** Now Hit the Pipe Cap that is on the Crankshaft (covered with the Pipe Cap). Repeat the Procedure Until the Flywheel can be Lifted Off the Crankshaft. *** Now Replace the Key Between the Flywheel and Crankshaft and Reverse the Procedure. Be Sure you have the Flywheel Torqued to at Least 00 - 00 Foot Pounds. The Key Times the Plug Firing and is Not Designed to Hold the Flywheel from Turning on the Crankshaft. The Flywheel Nut or Starter Clutch Torque Does that. 3- The Following is a General Instruction File for Setting the Valve Clearance on Non OHV Engines. **Remove the Carburetor and the Crankcase Breather/Vent and the Valve (Stem) Cover so you have Access to the Valve Stems, Springs and Keepers. Set 1 Cylinder to TDC on the Compression Stroke. Using a Blade Style Feeler Gauge, Check the Clearances. The Intake should be .005in - .007in and Exhaust .009in - .011in. If the Feeler Gauge will Not Slide Between the Valve Tip and the Tappet, then you Must Reset the Clearances. **You Will Require a Small Engine Valve Spring Compressor to Remove the Springs and Keepers from the Valve Stems.** Some Engines Use a Valve Keeper that is like Automotive Keepers (2 Cone Shaped Keepers that Set in the Valve Retainer/Rotocoil Assembly)and the Other Style is a Slotted Retainer that is Moved (once the Valve Spring is Compressed) to the Larger Opening in the Retainer and the Retainer Slips Over the Valve Stem Tip for the Valve to be Removed. Remove the Heads. Set 1 Cylinder so the Piston is at TDC on the Compression Stroke And Check the Clearances Between the Valve Stem Tip and the Tappet. The Clearances are as Follows: Intake Valve Clearance is .004in - .006in and the Exhaust is .007in - .009in. You have to Lightly Grind the Valve Stem Tip and Place the Valve Back Into the Engine (you can Hold the Valve Seated by Hand) and Check the Clearance Until you Reach the Required Clearances. Once the Valve Clearances are Reached, Re-Install the Valves on that Cylinder and Turn the Other Cylinder to TDC on the Compression Stroke and Set that Cylinders Valve Clearances.  Once that Cylinder is Set, then Re-Assemble the Engine.**  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