Small Engines (Lawn Mowers, etc.): Craftsman 21hp mower runs erratically, blown head gasket, carburetor body

Question
Hi, I have a Craftsman riding mover model 917.270950. I have had this mower running fine for +/- 7 years. Recently, the mower idle speed has begun to drop and recover erratically. I have changed the plugs, fuel lines, air filter, fuel filter, cleaned the gas tank cap vent, cleaned the breather, changed another fuel/vacuum line, and removed and cleaned the upper 1/2 of the carb. Still whenever the motor runs for a short while, it begins to idle erratically again. Do I need to remove the lower carb? or am I chasing my tail?

Answer
Hi Byron:

First Lets Eliminate the Carburetor as the Cause. It is the Most Common Cause for the Problem you Described.  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, 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 Accidental Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required. A Blown Head Gasket will Also Cause this Problem. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John

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Respectfully

John