Small Engines (Lawn Mowers, etc.): Loss of power, engine model type, engine numbers

Question
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.  Occasionally, the power returns for a short time then I lose it again.  Any ideas?

ANSWER: Please send the engine model, type and code number so I can look up some information.
Eric

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QUESTION: The model # is S2046.  Not sure what you mean by code #.  There is a OMGX10784L9 on the front of the manual.  I have also changed spark plugs without improvement.  It seems to run almost normally for a short time after start-up, then it seems to throttle down and lose speed after the engine gets warm.

Answer
There are some numbers on the engine, stamped in the valve cover, blower housing or on a sticker mounted on the engine.  The numbers are the engine model, type and code numbers.  I need to know if the engine is an L head or OHV.  I can look up the engine numbers to help solve your problem.
A flashlight can help you find the engine numbers.
Eric