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13 Kubota Zero Turn Problems (Troubleshoot)

When you own a Kubota zero-turn long enough, you’re bound to run into problems that need to be addressed before they develop into more serious problems. This is true of all mechanical products as mechanical items wear over time.

Keeping the mower clean and storing it in a dry location helps prevent corrosion from developing on the mower. Performing routine maintenance and using fresh gasoline will help reduce potential problems and extend the life of your Kubota zero-turn.

I have put together a list to help you troubleshoot and narrow down the cause of your mower problem. T These charts and links to articles will help address problems with Z121, Z231, Z421, Z422, Z726, Z781 an other zero turn models.

Follow the safety precautions listed in your Kubota operator’s manual to minimize injury while performing repairs. Always part your mower on a flat level surface, remove the ignition key, and remove the spark plug wire prior to performing repairs.

Common Kubota zero turn problems

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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.

Problem 1: Mower Won’t Start

A Kubota zero-turn won’t start when the engine doesn’t get the air, fuel, and spark required to form an explosion to start. The battery, starter solenoid, and switches can also fail and cause a starting problem.

For More Information Check Out:
Reasons a Kubota Zero Turn Mower Won’t Start

Potential CauseSolution
Empty fuel tankFill with fresh fuel.
Old fuelEmpty the fuel tank. Fill with fresh fuel and an additive to clean the fuel system like Sea Foam.
Bad spark plugReplace a dirty or damaged spark plug.
Plugged air filterClean a dirty air filter. Replace a very dirty or damaged filter.
Plugged fuel filterReplace the fuel filter.
Clogged fuel lineRemove and clean a clogged fuel line. Replace the line if needed.
Bad fuel pumpReplace a bad fuel pump.
Dirty carburetorRemove and clean the carburetor. Rebuild or replace if damaged.
Bad battery, loose cables,
or corroded terminals
Charge a weak battery. Replace a bad battery that won’t hold a charge. Secure cables and remove corrosion from components.
Bad safety switchReplace a bad safety switch.
Bad ignition switchReplace a bad ignition switch.
Bad starter solenoidTest and replace a bad starter solenoid.
Kubota Zero Turn Starting Problems

Problem 2: Mower Starts then Dies

Many of the items that cause a zero turn to not start are also reasons a mower will die after running. In addition to these items, you’ll also need to check for a plugged mower deck, bad ignition coil, and low or high engine oil level.

For More Information Check Out:
Reasons a Kubota Zero Turn Starts Then Dies

Potential CauseSolution
Old fuelDrain the fuel tank. Mix fresh fuel with a fuel additive to stabilize gas, reduce moisture and clean the fuel system. Add to the fuel tank.
Plugged air filterClean a dirty air filter. Install a new filter when it is very dirty or damaged.
Dirty cooling finsClean around the cooling fins and replace damaged fins.
Clogged fuel lineRemove a clogged fuel line and attempt to remove the clog. Install a new fuel line when you can’t remove the restriction.
Bad fuel pumpReplace a bad fuel pump.
Dirty carburetorRemove and clean a dirty carburetor. Rebuild or replace the carburetor when it can’t be sufficiently cleaned or internal parts are damaged.
Bad fuel cap / fuel tank ventReplace a fuel cap that no longer allows the fuel tank to vent through the cap.
Wrong engine oil levelCorrect the engine oil level by adding or removing a little oil until it is at the level recommended by the engine manufacturer. Consult a mechanic when this doesn’t solve the problem. The Kubota may have extensive engine damage.
Plugged mower deckScrape the mower deck. Sharpen the mower blades.
Bad ignition coilReplace an ignition coil that has a break in continuity.
Dirty spark plugInstall new spark plug(s) when they are dark in color, damaged, or worn. Clean them with a wire brush when they are in good condition and slightly dirty.
Kubota Zero Turn Starts, Stalls & Dies

Problem 3: Mower Won’t Move Forward or Reverse

The hydrostatic transmission pumps fluid to move the wheels. The pressure is so great that you will not be able to free-roll the zero turn without bypassing the transmission.

Make sure the transmission levers are not bypassing the transmission. Check the belt, pulleys, and tensioners to make sure they are securely in place and not damaged. Ensure the oil is fresh and at the full level.

For More Information Check Out:
Kubota Zero Turn Won’t Move Forward or Reverse

Potential CauseSolution
Transmission bypass levers in the wrong positionPlace the transmission bypass levers in the operating position. You will find a lever near each drive wheel.
Drive pump belt is wornReplace a worn belt and confirm it is sitting securely around the pulleys.
Bad tensioner pulleyReplace the tensioner pulley. Grease the tensioner arm.
Missing or damaged idler arm springReplace a broken or missing spring.
Low or old hydraulic oilChange your hydraulic oil at regular intervals as recommended by Kubota.
Check your hydraulic oil periodically to ensure your hydraulic fluid is full. (Note: some transmissions are unserviceable. Consult the Kubota dealer for help)
Kubota Zero Turn Mower Won’t Move Forward or Reverse

Problem 4: Mower Vibrates

Even if you have a seat suspension system, you still bounce around when mowing the lawn. When you develop a vibration, the shaking and bouncing can get worse.

Check for worn engine mounting bolts or a bad clutch. Inspect all of the linkages and remove all debris from the mower. Items on the mower deck can fail or wear causing pulleys and blades to wobble and the deck belt to become loose.

For More Information Check Out:
Reasons Your Kubota Mower is Vibrating

Loose or missing engine mounting boltsSecure the engine mount bolts. Replace any worn or missing bolts.
Failing clutchReplace a bad electric clutch. Replace a worn clutch cable, lever, or bushings on a manual engagement clutch.
Unbalanced or damaged mower bladesReplaced damaged blades. Make sure they are correctly balanced.
Foreign material wrapped around the blade shaftRemove foreign objects wrapped around the blade shaft. Inspect the spindle and housing for damage.
Bad spindle housing bearingsCheck the spindle bearings and replace them when worn.
Bad deck beltReplace a worn or loose deck belt.
Bad pulleysReplace damaged pulleys or pulleys where you feel restriction when turning by hand or a wobble due to a bad bearing.
Debris lodged in the mowerClean the mower checking all crevices for debris.
Kubota Zero Turn Vibration Problem

Problem 5: Mower Overheats

Engine oil plays an important part in keeping the engine cool. Use an air-cooled engine oil of the right viscosity that is high in zinc. Keep the engine oil level full.

Check for items that can block airflow around the engine including the cooling fins, engine shroud, and engine guard.

Inspect the air filter, mower deck, and mower blade condition.

For More Information Check Out:
Your Kubota Lawn Mower Engine Overheats

Potential CauseSolution
Wrong engine oilDrain the engine oil and fill it with fresh oil. Use a 10W-30 oil in most conditions. You may have to use a different viscosity in very warm conditions.
Low engine oil levelDrain the fuel tank. Refill with a fresh gas with an additive to clean the fuel system and stabilize the fuel.
Plugged engine cooling finsRemove the carburetor and clean it to remove deposits that m
MIssing engine guardReplace a missing engine guard. Securely attach a loose guard.
Plugged air filterReplace a dirty air filter.
Plugged mower deckScrape the mower deck to remove grass clippings and debris.
Dull mower bladesSharpen dull mower blades. Replace worn blades.
Overworking the engineSlow down the ground speed to match the mowing conditions. Avoid cutting wet grass. Double or triple-cut an overgrown lawn.
Kubota Zero Turn Overheating Problem

Problem 6: Mower is Smoking

A Kubota zero-turn smokes when the air filter is plugged, the engine oil is not correct, or a bad engine gasket has caused oil to seep onto a hot surface like the muffler.

When you can’t find the cause of the smoke, you may have internal engine issues like a worn piston ring or a burnt valve. In this case, I recommend having a small engine technician perform tests to determine the cause.

For More Information Check Out:
Why Your Kubota Lawn Mower is Smoking

Potential CauseSolution
Plugged air filterReplace a plugged air filter.
Too much engine oil Remove a little engine oil from the crankcase until it is corrected. Check the condition of the air filter.
Low engine oil levelHave a small engine technician inspect the engine. You can correct the engine oil level, but chances are the engine is damaged if it began smoking due to low engine oil.
Bad engine gasketLocate the bad engine gasket and repair it.
Internal problems: piston ring or valve trainIf you continue to experience engine smoking, a small engine technician must perform testing to determine the cause of internal engine damage.
Kubota Zero Turn is Smoking

Problem 7: Mower Has a Weak Hydrostatic Transmission

Hydrostatic transmissions on a Kubota zero-turn may experience a weak transmission when the hydraulic oil is old or the hydraulic tank is low on oil.

It can also feel weak when the drive belt or tensioner pulley is worn or broken.

Potential CausesSolutions
Bad drive beltReplace a worn pump drive belt
Bad tensioner pulleyReplace a bad tensioner pulley. Grease the tensioner arm.
Low or old hydraulic oilChange the hydraulic oil at regular intervals. Keep the hydraulic oil level at the full level.
Kubota Zero Turn has a Weak Hydrostatic Transmission

Problem 8: Mower Won’t Drive Straight or Steer Correctly

When a zero turn doesn’t drive straight and pulls to one side, check the tire pressures and dampers. If these items are in good condition, you may just need to track the mower so each tire rotates at the same speed.

Potential CauseSolution
Incorrect tire pressureEnsure the tires are filled to the manufacturer’s specifications. The tire pressures must be equal on each side of the zero-turn.
Bad dampersReplace with new dampers.
Tracking adjustment neededAdjust the speed adjustment bolt to change the rotation speed of the tire so each tire moves at the same speed. Refer to your owner’s manual.
Kubota Zero Turn Steering Problems

Problem 9: Mower is Running Rough and Sputters

When you find your Kubota zero-turn is running rough and bogs down, look for items that can restrict fuel flow or airflow or can cause an intermittent spark.

You’ll also need to look at items that can put extra load on the engine like a fast ground speed, plugged mower deck, and dull mower blades. Not having your throttle at its fastest speed can also cause the engine to run sluggishly when the blades are engaged.

For More Information Check Out:
Kubota Lawn Mower is Running Rough or Sputtering

Potential CauseSolution
Old fuelDrain old fuel. Refill with a gas and fuel stabilizer mixture.
Clogged fuel lineRemove a clogged fuel line and remove the clog using carburetor cleaner and compressed air. Install a new fuel line when the clog can’t be removed.
Plugged fuel filterReplace the fuel filter.
Dirty carburetorRemove the carburetor to clean it. Rebuild or replace it if needed.
Bad gas capReplace a gas cap that no longer allows the fuel tank to vent.
Dirty spark plugClean a dirty plug using a wire brush. Install a new one if it is very dark in color, worn, or damaged.
Fast ground speedSlow down the ground speed to match the mowing conditions. Slow down when mowing tall, thick, or wet grass so the engine isn’t under too much load.
Low engine speedPlace the throttle lever in its highest position when engaging the mower blades.
Plugged mower deckScrape the mower deck to keep it clean.
Dull mower bladesSharpen the mower blades.
Kubota Zero Turn is Running Rough

Problem 10: Mower Blades Won’t Engage

The mower blades won’t engage on a Kubota zero turn when the PTO switch is faulty, the battery is weak, a safety switch failed or the clutch is bad.

The blades won’t turn when the belt is worn or has fallen off the pulleys due to a stretched belt, bad pulley bearing, or worn tensioner parts.

For More Information Check Out:
Kubota Mower Blades Won’t Engage or Turn On

Potential CauseSolution
Worn mower deck beltReplace a belt that is worn, cracked, or has a shiny glazed appearance.
Belt falls off the pulleysReplace worn or damaged deck parts including a worn idler arm, worn spring, or bad pulleys. Replace a stretch mower deck belt.
Bad PTO switchReplace the PTO switch.
Bad clutchReplace the clutch. On a manual engagement clutch, replace a worn clutch cable, lever, springs, and linkages.
Weak batteryTest the battery and place it on a charger if the reading is less than 12.7 volts for a 12-volt battery. Replace the battery when it won’t hold a charge.
Bad Safety switchReplace the safety switch
Blown fuseReplace the fuse with the same capacity fuse.
Kubota Zero Turn Mower Blades Won’t Turn On or Engage

Problem 11: Mower is Leaking Gas

It can be difficult to find where a Kubota is leaking gas especially if the gas has evaporated into the air and doesn’t leave any wet spots behind.

Common areas to check for a leak is the carburetor and dry cracked fuel lines. You may also develop fuel leaks from fuel components from plastic components that degrade or seals that dry out.

For More Information Check Out:
Reasons Your Kubota Lawn Mower is Leaking Gas

Potential CauseSolution
Bad carburetor bowl gasketReplace the gasket located between the carburetor bowl and the carburetor.
Stuck carburetor float or float needleClean the carburetor and replace any damaged parts.
Cracked fuel lineReplace the fuel line.
Bad fuel tankReplace a fuel tank that begins leaking at the seams
Bad fuel shut-off valveReplace the fuel shut-off valve
Weak fuel filterInstall a new fuel filter.
Bad fuel pumpInstall a new fuel pump.
Bad gas cap sealReplace the gas cap. You may be able to purchase only the rubber seal on some caps.
Kubota Zero Turn is Leaking Gas

Problem 12: Mower Clicks & Won’t Turn Over

When the Kubota zero-turn just clicks when you go to start it, you may have a bad starter solenoid. In addition to the solenoid, check the items that can affect the power getting to the solenoid.

These include the battery, cables, terminals, and ground. When the fault doesn’t lie with any of these items, check the starter motor.

For More Information Check Out:
Kubota Lawn Mower Clicks & Won’t Turn Over

Potential CauseSolution
Damaged or loose battery cables & wiringReplace damaged cables. Remove any corrosion on the terminals or other components. Secure loose cables.
Weak or bad batteryTest the battery and place it on a charger if the reading is less than 12.7 volts for a 12-volt battery. Replace the battery when it won’t hold a charge.
Bad groundRemove corrosion from the ground. Make sure the ground cable from the battery and ground cable from the starter solenoid is making good contact. (A 3-post solenoid is self-grounded)
Faulty starter solenoidTest the starter solenoid and replace it if faulty.
Bad starter motorReplace a bad starter motor.
Kubota Zero Turn Mower Clicks & Won’t Turn Over

Problem 13: Mower Has a Bad or Uneven Cut

There are many items that can affect the cut quality of your Kubota zero turn. First, check the tire pressures to make sure you don’t have a low tire that is causing the deck to sit unleveled.

Next, at the condition of the components on the top of your mower deck and underneath the deck. Sharpen dull blades, replace components with bad bearings and replace a worn deck belt.

For More Information Check Out:
Reasons for a Kubota Zero Turn Bad or Uneven Cut

Potential CauseSolution
Dull or worn mower bladesSharpen the mower blades. Replace blades that are extremely worn where the blade sails are thinner than the center of the blade or the blade ends are worn and rounding.
Bent mower bladeReplace a bent mower blade.
Blade installed wrongMake sure the blades are installed with the correct hardware. The blade sails must be pointed upward toward the mower deck.
Bent blade spindleReplace a bent spindle. Inspect the spindle housing for damage.
Bad mower deck belt or bad pulleysReplace a deck belt that is stretched, worn, cracked, or has a glazed appearance. Slowly rotate the pulleys by hand. Replace the pulleys when you feel a restriction, hear a bearing noise, or the pulley is wobbling.
Mower deck is plugged with grass clippings & debrisScrape the mower deck.
Uneven tire pressureCorrect the tire pressures. Make sure they are even on the left and right-hand sides.
Unleveled mower deckLevel the mower deck so the mower deck is level side-to-side. The mower deck sits slightly lower in the front than in the rear. Consult the operator’s manual for exact specifications to level the deck.
Engine speed is too lowWhen engaging the blades, have the throttle set at the highest level.
Ground speed is too fastSlow down when mowing thick, wet or tall grass. Mowing in these conditions puts extra strain on the engine. Running the mower too fast can end up pushing over some grass instead of cutting it.
Operator errorProperly overlap paths so strips of grass are not left in between passes. Use a small format deck like a push mower to mow ditches and other steep changes in grade.
Kubota Zero Turn Has a Bad or Uneven Cut