Small Engines (Lawn Mowers, etc.): Loss of power - Scotts riding mower, twin cylinder engines, valve clearance

Question
I have a Scotts riding mower with B&S engine.  It was running fine and while cutting I noticed a loss of power and it started using almost twice as much gas to cut the lawn.  So far I have changed the air, fuel and oil w/filter. I've also changed both the drive and mower belts and spark plugs.  Occasionally, the power returns for a short time then I lose it again.  Any ideas?

Answer
Hello Steve:

If the Pulleys and Idlers are in Good Shape and are Not Grinding or Roaring, then the Deck Should Not be the Cause. If this is an OHV Engine. The First Thing is the Valve Settings. 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). Set the Cylinder you are Setting the Valves on to Top Dead Center (Both Rocker Arms will have Play in them when the Engine is at TDC) When Setting the Valve Clearance. 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. 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 and Type Numbers. Then Double Click on the Model in the Results Area. Now you can Select the Section of the Engine you Wish to View. Send me the Model and Type Numbers Off the Engine and the Mower Model Numbers, Please. With these I can Locate the Proper Manual and Better Assist you. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. 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 9pm EST (US). My New Day Starts then. Thanks.

Respectfully

John