How to Adjust a PTO Clutch on a Lawn Tractor

Many lawn tractors, particularly John Deere riding mowers, use a PTO clutch. The PTO function is what engages the mower blades of the lawn tractor. The mower's battery sparks the PTO clutch, which then guides the shaft and rotates the blades of the mower. However, if your lawn mower is not working at its best capacity, it may need to be adjusted or replaced. There are two main ways to tell if your PTO needs adjusting. By adjusting the PTO clutch, you can ensure the best quality, most efficient and safest lawn mowing.

Aerial view of lawn tractor or riding mower. Directly above. Drone view.
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How to Adjust a PTO Clutch on a Lawn Tractor

What Is a PTO Clutch on a Lawn Tractor?

A PTO clutch is a switch or lever found in tractor engines and stands for "power take off." It can be run by a belt or shaft. Typically in larger lawn mower engines, the PTO clutch is shaft-driven. The operator of the lawn tractor engages the mower blades using the PTO clutch.

How Will You Know Your PTO Clutch Needs Adjustment?

As the lawn tractor engine ages, the PTO clutch can start to slip. This causes the mower deck to cut less efficiently and at a lower quality. If you notice a rapid decline in the standard of your mowing, it could very well mean your PTO clutch needs adjustment.

Another sign your PTO may need checking out is if the mower in your lawn tractor is unresponsive. This could be a sign that the PTO clutch has stopped engaging the mower blades.

How to Adjust Your Lawn Tractor’s PTO Clutch

Firstly, you'll need to ensure your lawn mower is parked on a flat, even surface. The parking brake must be on and the ignition must be off. For safety, you must also ensure that the PTO switch is in the "off" position.

To find the PTO clutch, check the crankshaft under the engine. On the clutch plate will be a sticker, informing you if the clutch is Warner or Ogura. If the sticker says Warner, you'll want the feeler gauge at 0.51mm. If it says Ogura, the feeler gauge should be at 0.41mm.

In the brake plate directly above the pulley, there should be a slot. Insert your feeler gauge through this slot so the gauge is between the armature and the clutch rotor. Keeping the feeler gauge under the bold directly, tighten the three lock nuts, one at a time.

Using a sweeping motion with your feeler gauge, tighten the first nut until you can feel adequate friction between the clutch rotor and armature. Then, repeat this step with the second and third nut.

Finally, start up the engine again and check the PTO's engagement of the rotor blades. You may need to tighten or loosen the nuts again in order to get the exact engagement you need.