Small Engines (Lawn Mowers, etc.): Kohler engine running rough, blown head gasket, high pitch sound

Question
I have a 10 hp Kohler horz shaft (Cub Cadet) model #KZ241AQS serial #6404226. After it has run awhile it looses power and rpms go up and down, also makes a high pitch sound like a blown head gasket. Have ground valves and set them, set points. If you rev engine up from idle it seams to spray gas out of card a little and will sometimes backfire thru carb. Have replaced head gasket when doing valves, also doing the valves it didn't make any difference in the running. Could there be a crack in the head that opens when engine gets hot. When engine is cold it has a lot of power and cuts grass at half throt. until engine gets hot. Can you help me out.

Answer
Hello Rich:

What is the Compression of this Engine both Cold and then Hot when the Power Loss Occurs? From your Description it Sounds like the Rings are Stuck or are Worn to a Point that they are Not Expanding with the Cylinder Properly. A Crank in the Head would be Noticeable from the Start. I have Never Seen a Head Cracked that Did Not have Problems Idling. You can View a Breakdown/IPL of this Unit at this Site Addy; http://www.jacobisalespartslookup.com/home.asp and Select the Cub Cadet Logo. Now Select Shop Online Parts Look Up. Now Select the OEM ( Cub Cadet) and Select the Model Tab. Then Enter the Model Numbers and Click Search. Then Double Click on your Model in the Results Area. Then Select Sectional View. Then Select the Section of the Unit you Wish to View. You can View a Breakdown of the Engine at this Site Addy; http://www.kohlerplus.com/login.asp and Select Enter as Guest. Now Select the Thumbnail of the Catalog you Wish to View. 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