Park the riding mower on a flat, even surface and cut the engine. Wait until the mower completely cools. Open the engine hood.

Find the spark plug at the side of the engine assembly under the hood. Disconnect the black ignition wire from the back of the spark plug.

Ensure the PTO lever is disengaged. Adjust the mower deck lever so that the deck is set into its lowest possible position.

Ensure the spark plug is disconnected. Remove the plug wire from the rear of the spark plug. You can find this spark plug on the side of the mower’s engine assembly.

Find the mower’s PTO clutch on the underside of the engine. It is in a compact bell housing. The riding mower’s belt also winds around the clutch.

Use a brush wire to clean any debris and build-up off the PTO clutch. Wipe it down with a dry cloth.

Observe the long, slender rectangular PTO clutch openings. There are three of these. Insert a feeler gauge into each adjustment slot and see if there is any measurable distance between the two parts that exist on either side of the gauge. The armature face and the rotor here should be touching either side of the feeler gauge.

Find the adjustment bolt on each adjustment slot and tighten it using a socket wrench if the armature face and rotor within the slots were not touching the feeler gauge. Take care not to tighten the bolt too greatly, as the armature and rotor should only just touch the gauge.

Tighten or loosen the adjustment bolts on each of the other two adjustments slots if necessary. These will likely require adjustments if the initial adjustment slot needed tweaking.

Reinsert the plug wire into the rear of the spark plug. Shut the mower’s engine hood.

Power on the mower and engage the PTO clutch. If the blades do not engage, take the mower into your local lawn care shop or contact your mower manufacturer. The PTO clutch may need to be replaced.