10 Common Kubota Lawn Mower Problems (Troubleshoot)

Wouldn’t it be great to own a lawn mower that never requires maintenance and never breaks down? Unfortunately, that mower does not exist. While Kubota manufactures high-quality lawn mowers, their mowers are subject to problems over time just like all lawn mowers on the market.

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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.

Common Kubota Lawn Mower Problems & Solutions

Won’t Start

There are many reasons why a Kubota lawn mower won’t start. Start identifying the issue by looking for an air or fuel restriction.

Check for a plugged air filter, sufficient fuel supply, clogs in the fuel components, or a plugged fuel filter. Old gas that has been running through the mower can be the cause of your clogged or failing fuel components.

Next, check your spark plugs and ignition coil. Without spark, your mower will not start. Continue checking your battery, safety switches and charging system to ensure they are all working correctly. Make sure all wires are securely attached and making good connection.

Detailed information can be found at:
Reasons Your Kubota Lawn Mower Won’t Start

Cause	Reason for Problem	Solution
No gas in the fuel tank	Fuel tank is empty	Fill with fresh fuel
Bad or old fuel	Fuel breaks down overtime making your fuel less efficient and prone to clogging the fuel system	Drain the fuel tank and fill with fresh fuel. Use a fuel additive like Sea Foam to stabilize the fuel and assist with cleaning the fuel system. Use the right fuel.
Faulty or clogged fuel cap	The vent in the cap can get clogged causing your tank to form a vacuum restricting fuel flow	Use a thin piece of wire to try to clear the clogged vent. Replace the cap if needed.
Bad spark plug	Excessively dirty or broken spark plug; bad connection; not gapped correctly	Replace with a new spark plug, secure connections and ensure it is gapped to manufacturer specifications
Plugged air filter	Dirt and grass can plug the air filter preventing air flow	Remove the filter and clean it. Replace the filter if it is in bad condition.
Plugged fuel filter	A dirty fuel filter will restrict fuel flow	Replace the fuel filter
Bad fuel pump	A failed or leaking fuel pump will no longer create pressure needed to pump fuel	Replace the fuel pump
Blocked fuel lines	Bad fuel deposits and dirt can build up and clog the fuel lines preventing the engine from getting the required fuel	Use a carb cleaner and compressed air to clear the clog out of the fuel line. Replace line if necessary.
Dirty carburetor	The carburetor can become dirty and clogged due to bad fuel and ethanol deposits preventing fuel flow	Clean the components making up the carburetor. Replace if needed.
Bad battery or loose & dirty terminals	A dead battery, loose cables or corroded terminals can cause starting problems	Charge your battery and replace if it won’t hold a charge. Make sure your cables are tight and clean the corrosion from terminals.
Bad safety switch	Safety switches is a safety measure that exist to prevent your mower from starting in certain situations. When a switch fails, your mower may not start.	Test and replace faulty safety switch
Bad ignition switch or coil	Your mower will not start when either the ignition switch or coil is bad	Test and replace a bad switch

Starts and Dies

Many of the items that prevent a Kubota mower from starting can be the same as those that cause it to die. When your mower isn’t able to get the air, fuel, and spark it requires, it will run sluggish and possibly quit.

Overheating can cause your Kubota mower to die. It’s important to use the correct engine oil; maintain the correct engine oil levels; and clean your engine cooling fins and around the engine, so air can circulate around your them to keep the engine cool.

The electrical system or clogged mower deck can also cause your mower to die after it has been running. Check the charging system, switches, ignition coil, and spark plugs.

Detailed information can be found at:
12 Reasons a Kubota Lawn Mower Starts Then Dies

Reason for Problem	Solution
Fuel breaks down overtime making your fuel less efficient and prone to clogging the fuel system and engine damage	Dirt and grass can plug the air filter preventing airflow
Cooling fins get packed with dirt, oil, and grass not allowing air to effectively cool the engine block	Remove the filter and clean it. Replace the filter if it is in bad condition.
Cooling fins get packed with dirt, oil and grass not allowing air to effectively cool the engine block	Replace broken fins and clean the cooling fins.
Bad fuel deposits and dirt can build up and clog the fuel lines preventing the engine from getting the required fuel	Use a carb cleaner and compressed air to clear the clog out of the fuel line. Replace a plugged fuel filter.
The carburetor can become dirty and clogged due to bad fuel and ethanol deposits preventing fuel flow	Clean all components making up the carburetor. Replace if needed.
Too much engine oil increases pressure in the crankcase causing it to overheat and die	Correct your engine oil level by removing a little oil
Windings on the coil can separate and short out on a bad ignition coil	Clean or replace spark plugs if needed. Ensure spark plug wires are securely attached and the plug is gapped correctly.
A windings on the coil can separate and short out on a bad ignition coil	Check for a break in the continuity using an ohm meter and replace is found bad
A choke is used for cold starts. The choke can cause your engine to shut off when it continues to restrict airflow after the engine warms.	Make sure the choke is in the correct position
A battery that doesn’t hold a charge or a bad charging system that can’t keep the battery charged will cause your Kubota to die after running.	Test your battery and charging system. Replace any electrical components found to be bad. Read more about testing your battery and charging system here.
Gas caps have vents for air to pass through. When the vents get clogged, the fuel tank will cause fuel restrictions.	Replace a fuel cap that no longer vents
A clogged mower deck causes a strain on the engine causing it to work hard and possibly shut down	Periodically scrape your mower deck to keep it clean

Mower is Smoking 

Seeing smoke coming from your Kubota lawn mower can be quite alarming. A Kubota mower may start smoking when the air filter is clogged or the choke setting is incorrect restricting airflow.

This causes your engine to run rich allowing a higher concentration of fuel to burn creating a black smoke.

It can also begin smoking when there is an insufficient engine oil level or internal engine problem including piston ring failure, valve train problems, and gasket failure. The oil that drips onto your muffler or is spilled on your engine during an oil change will burn off also causing your Kubota to smoke.

Detailed information can be found at:
Why Your Kubota Lawn Mower is Smoking

Cause	Reason for Problem	Solution
Plugged air filter	Drain a little engine oil until it is at the manufacturer’s recommended oil level.	Remove the filter and clean it. Replace the filter if it is in bad condition.
Too much oil in the crankcase	Excessive oil can cause pressure to build in the engine allowing oil to get into the cylinder through the valve train	Bring to a small engine repair shop to inspect engine damage. You can try adding oil, but it is often too late to this fix your engine problem.
Engine oil level is too low	Lack of oil can increase friction in your engine causing extreme heat.	Internal problems including the piston ring, valve train, or engine gasket
Internal problems including the piston ring, valve train or engine gasket	Internal engine problems can have a detrimental effect on your mower if they are not caught soon enough and fixed.	Bring your Kubota to your local small engine repair shop for troubleshooting

Kubota Lawn Mower Has a Weak Hydrostatic Transmission 

Cause	Reason for Problem	Solution
Bad drive belt	A bad drive belt can cause your pump not to work efficiently	Replace a frayed, cracked or worn belt
Bad tensioner pulley	When a tensioner pulley fails, it fails to keep tension on the drive belt	Replace the pulley and grease the tensioner arm
Low or old hydraulic oil	Low or old hydraulic oil can fail to lubricate the hydraulic system causing your hydraulic system to seem weak	Change your hydraulic oil at regular intervals as recommended by Kubota. Check your hydraulic oil periodically to ensure your hydraulic fluid is full. (Some transmission systems are sealed and they can’t be serviced. If you are having trouble with a sealed system, see your dealer).

Won’t Drive Straight or Steer Correctly

It can get frustrating when you are always having to adjust the operation of your mower because it is pulling to the right or left. Here is a list of items to check on a zero-turn or riding lawn mower to make the necessary corrections to get your mower to drive straight.

Cause	Reason for Problem	Solution
Incorrect tire pressure	Unequal tire pressure can cause your mower to pull to one side.	Adjust the speed adjustment bolt to change the rotation speed of the tire. Refer to your owner’s manual.
Bad dampers on zero turn	Bad dampers will cause your mower to jerk to one side when moving forward	Replace with a new damper
Tracking adjustment needed on zero turn	When one tire is moving faster than the other, your mower can pull to one side	Worn bushings, washers, and gears can cause your mower to not steer one way or the other
Worn or loose steering components in riding mower	Worn bushings, washers and gears can cause your mower to not steer one way or the other	Inspect and replace the parts that failed on your steering system

Mower Won’t Move

Detailed information can be found at:
9 Reasons Your Mower Won’t Move or Go Forward

Cause	Reason for Problem	Solution
Drive release lever in the wrong position	The drive release lever allows hydrostatic mowers to roll freely	The drive release lever must be in the operating position.
Missing key in the axle	Your riding mower may have a small key in the axle that may have fallen out of place	Replace the key in the axle
Drive pump belt is worn	The mower won’t move if your drive belt has fallen off. It could also not move if the belt is worn.	Replace a worn or cracked belt. Make sure the belt is securely around the pulleys.
Bad tensioner pulley	The bearing in the tensioner pulley can fail	Replace the tensioner pulley
Missing idler arm spring	If the idler arm spring breaks or goes missing, it can no longer place tension on the drive belt	Replace the broken or missing spring
Low or old hydraulic oil	Low or old hydraulic oil can fail to lubricate the hydraulic system causing your hydraulic system to seem weak	Let your hydraulic oil cool. If you find your mower runs fine when it is cold, but becomes weak when the hydraulic system gets hot, have your mower checked at your local Kubota dealership.
Hot hydraulic fluid	Hot hydraulic fluid can be a sign of damage to your hydrostatic transmission system	Follow Kubota’s procedures for changing the hydraulic fluid and bleeding air from the system in your owner’s manual.
Air in the hydraulic system	Air must be bled from the hydraulic system after changing your hydraulic fluid or the mower will not be able to move at normal speeds	Follow Kubota’s procedures for changing hydraulic fluid and bleeding air from the system in your owner’s manual.

Mower is Vibrating

Mowing isn’t the most comfortable task even if you do have one of those comfortable seat suspension systems on your Kubota lawn mower. Your comfort level can quickly deteriorate when your mower starts to vibrate and shake excessively.

A Kubota lawn mower can begin vibrating when the clutch bearing fails; the engine mounting bolts are worn; the mower blades are unbalanced; the spindle bearings or pulley bearings have failed; the deck belt is worn or debris is lodged in your mower.

Don’t overlook the small stuff. Something as small as an acorn or stone stuck in your mower can cause a significant vibration.

Detailed information can be found at:
How to Stop Your Lawn Mower from Shaking & Vibration

Cause	Reason for Problem	Solution
Loose or missing engine mounting bolts	Engine bolts are used to reduce vibration of the mower when the engine is running	Secure engine bolts and replace any missing bolts
Clutch is bad	When there is bearing failure and it falls out of the clutch it can cause vibration. A manual engagement clutch can have a bushing and linkages that can fail.	Replace the clutch
Unbalanced or damaged mower blades	Damaged and unbalanced blades can send a vibration through your mower. Blades must be balanced before installing	Replace any damaged blades and make sure they are balanced.
Material wrapped around the blade spindle	Foreign materials like string or long weeds can get wrapped around your blade shaft causing vibration	Remove all debris and items wrapped around the blade shaft. Check for spindle damage.
Bad spindle housing bearings	Vibration can be caused by a bad bearing in the spindle housing.	Replace bearing in the spindle housing or replace the whole spindle housing assembly
Worn pulleys or deck belt	Check deck belt and pulleys for wearing of the belt and bearing failure in the pulleys	Replace any damaged or worn belts and pulleys
Debris lodged in mower	The smallest little things can cause your Kubota to excessively vibrate. Check over your mower for debris stuck in the deck or mower. Don’t overlook the small stuff.	Check over your mower deck and mower for any place small items can be stuck in your mower. Remove these foreign materials.

Bad or Uneven Cut

Kubota mower decks normally give a nice cut. The quality of cut can suffer with a bent, worn or unbalanced mower blade; an unleveled mower deck; a low tire; a clogged mower deck; worn spindle or pulley bearings; or a worn belt.

Operator error can also contribute to your bad cut. Not overlapping your mowing paths correctly or operating your mower at a fast ground speed or low engine speed can also affect your Kubota mower’s cut quality.

Detailed information can be found at:
Reasons Your Kubota Lawn Mower Cuts Uneven

Worn mower blade	Uneven tire pressures	Engine speed is too low
Bent mower blade	Unleveled mower deck	Ground speed is too fast
Blade installed wrong	Bent blade spindle or spindle bearing	Damaged deck shell
Clogged Mower Deck	Worn deck pulleys or belt	Operator error

Leaking Gas

When gas evaporates into the air, it can often be hard to find the place your Kubota lawn mower is leaking gas. A Kubota mower can leak from its fuel components including the fuel filter, fuel pump, fuel lines, fuel shut-off valve, and fuel cap.

Detailed information can be found at:
Your Kubota Lawn Mower is Leaking Fuel

Cause	Reason for Problem	Solution
Dirty of Failed Carburetor	The carburetor can collect a buildup of substances remaining from old gas that can cause blockages or parts failures	Clean the carburetor and replace any damaged parts
Old Fuel Filter	Filter can become plugged	Replace fuel filter
Bad Fuel Pump	Pump can wear and deteriorate over time and may begin leaking at the seams	Replace the fuel pump
Bad Fuel Tank	A metal tank can develop a rust hole. A poly tank can leak at the seams of the tank.	Replace the fuel tank. Sometimes, a rust hole can be repaired if you can no longer find a replacement tank.
Bad Fuel Shut-Off Valve	Metal and plastic shut-off valves are prone to leaking	Replace the shut-off valve
Cracked Fuel Lines	Rubber fuel lines become dry and cracked causing gas to leak	Replace the fuel lines
Bad Seal in the Gas Cap	The gas cap seal can fail and no longer seal allowing gas to splash out of the fuel tank around the gas cap	Replace the gas cap