Small Engines (Lawn Mowers, etc.): Fouled plugs 18 hp Kaw., mixture adjustments, fuel mixture

Question
I have a 18 HP Kaw engine on a John Deere mower.  The drive part of the mower seems to work fine but the deck will not reach full RPM.  I replace the plugs and everything is fine but for only an hour or two.  Replace the plugs and fine again.  What is causing the plugs to foul so soon?  The plugs are dry but black.  The problem happens if th engine is hot or cold.

Answer
 Hello Mike:

 The Carburator is Too Rich. If it has the Fuel Mixture Screws in the Carburator, then Turn the One in the Bottom of the Bowl IN while Holding the Engine at Full Throttle. 1/4 Turn May be All that is Required to Lean Out the Carb Enough to Increase Engine Speed and Stop the Plugs from Fouling. If No Mixture Adjustments, then Clean and Rebuild the Carburator. Send me the Model Numbers Off of the Engine and I can Better Assist you. Hope this Helps. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John