Small Engines (Lawn Mowers, etc.): mower surges and will not idle at low speed, twin cylinder engines, craftsman model

Question
craftsman model 917.273022  -- 20 hp 46" mower kohler twin   garden  tractor..  mower will only start if set at high speed and full choke, will not stay running at lower speed ... it surges when it runs ,fast,slow,fast,slow.and its  starting to backfire when i shut it down... HELP !!!!

Answer
Hello Stan:

Check the Compression. You May have a Dead Cylinder. I Can Not Locate a Kohler Model CV20S-65551. I Did Locate a Kohler Model CV20S-65561. This is an OHV Engine. The OHV Engine OEM have been having Problems with the Valve Settings Moving and Causing Running Problems. If you have a Dead Cylinder, then Check the Valve Clearance and Set if Required. 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). Now Loosen the Valve Adjuster Locks and Set the Intake Valve Clearance to .004in -.006in and the Exhaust to .008in - .010in. I have had Better Performance Out of the Mowers and Less Burnt Valves Using these Settings. If the Valve Clearance is Good and the Compression is Low, then Remove the Cylinder Head and Inspect the Head Gasket and Check the Valves for a Burnt Valve Seat. You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.smallenginepartswarehouse.com/parts.asp and Select the Shop Online Parts Look Up. Then Select the Model Tab. Then Select the OEM and Enter the Model Numbers CV20S-65561. Then Double Click on the Model in the Results Area. Now you can Select the Section of the Engine you Wish to View. If the Both Cylinders Compression is Within 6opsi of Each Other, then  Remove, Disassemble and Soak 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, Float Pin, Float 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 Accidential Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John