How to Set a Mower Deck

Position the mower on level, hard ground where you can take accurate measurements between the ground and the mower blades. Set the parking brake so the mower does not move, and disconnect the spark plug wire from the spark plug to ensure the mower cannot turn on.

Check the tire pressure in each tire with a tire pressure gauge. If needed, add air to the tire with a manual tire pump. You can determine the exact pressure needed by looking at the sidewall of the tire. The pressure needed is listed in psi, or pounds per square inch.

Position the mower blade so the ends face the sides of the mower deck. Measure downward from the tip of each edge to determine how high the tip of the blade rests off the ground. Determine the difference between each side. Any distance greater than 1/8 inch requires adjustment.

Locate the adjusters on each side of the mower, and then adjust one side of the mower deck up or down until you reach the required tolerance. This is one step where each mower is slightly different. In most cases, the adjusters are near the mounting brackets that hold the mower deck onto the lawn tractor.

Rotate the mower blade so the blade faces front to back. Take a measurement off each mower blade tip. The back of the mower must be ¼ inch higher than the front. If the deck is outside tolerance, you must adjust the deck.

Locate the adjustment rod protruding from the front or back of the mower, depending on your brand and model. The rod is usually threaded and has two nuts. The outside nut is a jamb nut and the inside nut is the adjuster nut. Loosen the jamb nut and move the adjuster nut to raise or lower the deck until you are within tolerance. Tighten the jamb nut.