The more expensive lawn tractors in the John Deere line come with an electric PTO clutch. The PTO clutch is bolted to the bottom of the engine on the crankshaft, when the mower blades are turned to the ON position, a 12-volt current is sent to the clutch. A brake is engaged causing the blade belt to turn. As the engine ages, the clutch can start to slip, causing the mower deck to cut poorly, and when this happens you need to adjust the clutch.
Park the lawn mower on a hard, level surface and set the parking brake. Turn the ignition key to the OFF position. Ensure the PTO switch on the right of the dash is in the OFF position.
Locate the PTO clutch under the engine, bolted to the crankshaft. Check the sticker on the clutch plate; it will say either Warner or Ogura. Set the feeler gauge to 0.51mm if it is a Warner clutch and 0.41mm if it is an Ogura.
Insert the feeler gauge through the slot in the brake plate directly above the pulley; the gauge should be between the clutch rotor and the armature. Tighten one of the three lock nuts; ensure the feeler gauge is directly under the bolt. Tighten the nut and use a sweeping motion with the feeler gauge until there is friction between the armature and rotor. Repeat this step with the other two lock nuts.
Start the lawn mower and engage and disengage the mower blades to check the adjustment.