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Why Your Kubota Zero Turn Won’t Move Forward or Reverse

Your zero-turn may have stopped moving and you’re not sure why. I’ve put together a list of items to look at when troubleshooting the problem. Don’t attempt to tow your mower or you could end up damaging the transmission.

A Kubota zero-turn won’t move forward or reverse when the drive release levers are in the operating position, the hydro belt is worn, the tensioner pulley is bad, the idler arm spring is missing, the hydraulic oil level is low or hot, or air is trapped in the hydraulic system.

Take safety precautions when working with your mower’s hydraulic system. Wait for the transmission to cool and be careful working with hot hydraulic fluid.

Remove the ignition key and spark plug wires before performing any repairs or maintenance.

Kubota zero turn won't move forward or reverse

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

7 Reasons a Kubota Zero Turn Won’t Move Forward or Reverse

Drive Release Levers Not in the Operating Position

If you had to manually move the mower by pushing it, you would have had to release the hydros by placing the transmission bypass levers in the “bypass” position.

A zero-turn won’t move when the hydro levers are not engaged to power the wheels. You will find rods (Z100, Z200, and Z400 series) or levers (Z700 series) located on the left and right-hand sides of the zero-turn.

Make sure these levers are placed in the operating position so you are able to move the mower using the drive levers.

Pump Drive Belt is Worn, Loose, or Broken

A worn drive belt can affect the movement of your zero-turn. Check the drive belt to make sure it hasn’t fallen off and is positioned correctly and securely around the pulleys.

If the belt shows any signs of wear, it should be replaced.

Bad Tensioner Pulley

The bearing in the tensioner pulley or the pulley itself can break. Most tensioner pulleys are made of hard plastic which can wear over time or break.

Replace a pulley that is worn or has a bad bearing. Keep the tensioner arm greased so it is able to freely move and does not seize.

Missing Idler Arm Spring

The idler spring places tension on the pump drive belt. Replace the spring if it is broken or has fallen out of your Kubota.

Low Hydraulic Fluid Level

Consistent hydraulic fluid changes must be completed to keep your transmission system running at its best. Running the transmission with old or low hydraulic fluid can cause your zero-turn to not move or seem very weak while running.

Always check the fluid level before using the mower while the oil is cool. Wipe around the caps before removing them to check the fluid.

Dirt is often a factor in a failed hydraulic system so you want to take all precautions to not contaminate the system.

When your hydraulic oil is low, add more hydraulic fluid until the fluid level reaches the full level on the dipsticks or overflow tanks (depending on your specific model).

The hydraulic fluid in a zero-turn must be changed at regular intervals to keep the hydraulic system operating at its best.

Kubota Zero Turn ModelCapacityTransmission Oil
Z121SKH, Z122EBR, Z122RKW, Z125SKH5.1 QtsSAE 20W-50
Z231BR, Z231KH, Z231KW, K251BR, K251KH5.1 QtsSAE 20W-50
Z411KW, Z421KW, Z421KT5.1 QtsSAE 20W-50
Z723KH, Z724KH, Z725KH6.3 QtsParker HT-1000
Z724XKW, Z726XKW, Z751KWi, Z7817 QtsParker HT-1000
Kubota Zero Turn Transmission Oil & Capacities

It’s also a good idea to check for hydraulic fluid leaks when you find your hydraulic oil level is low. Contact your Kubota turf dealership for assistance with hydraulic fluid leaks.

Hot Hydraulic Fluid

When you operate a zero-turn with bad hydraulic fluid or low fluid, the oil is not able to efficiently lubricate the hydraulic system causing increased friction and overheating of the hydraulic fluid.

Hot hydraulic fluid in your mower can also be the result of more extensive damage.

I highly recommend taking your lawn mower to your local dealership if you experience leaking from the hydraulic pump or your mower runs fine when it is cold, but stops running when it gets hot.

Air in the Hydraulic System

Air trapped in the hydraulic system can cause your zero-turn to move slowly or not move at all. After changing the hydraulic fluid or any time you open up the transmission, you must bleed the air out of the system.

Air trapped in the system can cause the zero-turn to be noisy when it moves. It can also cause the oil to get hot and expand more than normal.

Removing air from the hydraulic system:

On most Kubota zero-turns, air can be removed from the hydraulic system by raising the rear drive tires off the ground. If you are unable to raise the drive tires, you can perform the test in an open area free of obstructions.

Make sure there is sufficient oil in the transmission before performing this procedure.

Open the bypass valves, remove the parking brake if it is on, and start the engine. Move the drive levers slowly forward and then reverse about 6 times.

Close the bypass valves. With the throttle at high, move the drive levers forward and reverse about 6 times. Repeat this process until you don’t hear excessive noise and the tires move at normal speeds.

Once the air has been removed, shut off the engine and engage the parking brake. Check the expansion tanks to ensure the oil is at the FULL COLD line. If not, add oil until it is up to this line.