12 Reasons a Kubota Lawn Mower Starts Then Dies

I don’t know about you, but I have experienced times when my mower was sitting in the middle of the lawn dead. It was either due to my son not checking the fuel level before he started mowing or because a part failed.

A Kubota lawn mower will start then die from old fuel, a plugged fuel filter, clogged fuel lines, a dirty carburetor, a plugged air filter, a bad fuel cap, a bad spark plug, a faulty ignition coil, a plugged mower deck or insufficient engine oil level.

Always take safety precautions as outlined in your operators manual including:

• Remove the ignition key and spark plug wires when working on your mower.
• Take caution when working around a hot engine.
• Wear eye protection to avoid getting fluids or dirt in your eyes.
• Protect your hands from sharp components.

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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.

Reasons a Kubota Lawn Mower Starts Then Dies

Bad or Old Fuel

Old gas will affect how your gas-powered Kubota lawn mower will run. It can be the root cause to your mower starting and then dying. This is because gas can cause corrosion and gumming of the fuel system.

Most gasoline you find at the fuel station will contain ethanol. This is a product added to gas to make it more environmentally friendly. That’s because ethanol is made from a high-starch plant like corn.

This fuel is better for the environment, but it is not good for the small engine on your Kubota. Ethanol attracts moisture from the air that accelerates corrosion and leaves behind a varnish that can restrict fuel flow. When the engine isn’t getting sufficient fuel, it will run sluggish and possibly shut down.

Because gas can begin to break down and become less effective as quickly as 30 days after purchase, it’s important to consume fuel within this time.

If you purchased more gas than you will consume or you want to take extra precautions to keep the fuel system clean and the gas stable, add a fuel stabilizer.

A product like Sea Foam Motor Treatment or STA-BIL will keep your fuel stable for a longer period. Stabilizers will keep the fuel stable from 30 days up to 2 years. Read the information on the product to determine how long the additive you choose will keep gas stable.

I choose to use Sea Foam in every tank of fuel. Read more about its advantages in “Use Sea Foam Additive in a Lawn Mower to Stabilizer Your Fuel“.

Solution: When you find the gas is old, drain the fuel tank using a fuel siphon pump. Refill your tank with fresh fuel. Add a fuel additive to stabilize your fuel, reduce moisture and clean your fuel system.

Plugged Air Filter

The air filter is a maintenance item that can keep your Kubota from continuing to run. Because of the dusty conditions created when mowing, the air filter can become plugged when it isn’t regularly changed or replaced.

The air filter protects the engine and reduces wear from particles that enter the air intake. Always run your mower with a clean air filter. Failing to do so can cause the mower to overheat and shut down subjecting the mower to additional damage.

It is good practice to replace the air filter annually and regularly clean it throughout the mowing season. You should check the filter before each mowing. It only takes a minute or two to check it.

Solution: Remove the air filter from its housing and check it for dirt buildup. Follow these steps to clean the air filter:

Clean a Kubota Paper Air Filter Element:

• After removing the air filter, wipe the remaining dirt from the housing and air filter cover. Be careful not to let dirt fall into the air intake.
• Tap the filter lightly against a solid surface to loosen and remove as much dirt as possible.
• Hold the filter up to a light source to check if you can see light shine through the filter. If you can, go ahead and reuse your air filter. If you cannot or the filter is covered in oil or damaged, you must purchase a new filter.
• Install the air filter and reinstall the cap on the filter housing.

Plugged Fuel Filter

A Kubota lawn mower uses a fuel filter to strain the fuel. It prevents dirt and other contaminants from entering the fuel system. Dirt and gummy deposits from your fuel can plug your fuel filter over time.

It’s best practice to replace your fuel filter annually to avoid most fuel filter issues during the mowing season.

Solution: If you find your fuel filter is plugged, remove it and replace with a new filter. You will find an arrow on the side of your fuel filter.

Make sure this arrow is pointed in the direction of the mower’s fuel flow. This means a correctly installed fuel filter will point toward the carburetor and away from the fuel tank.

Clogged Fuel Lines

The gummy deposits that are left behind when running old fuel can clog your fuel lines preventing fuel from continuing to run through the fuel system. This can cause a Kubota mower to die while mowing.

Check each section of the fuel line by shutting off your fuel flow using the fuel shut-off valve located at the bottom of your fuel tank. You can also use pinch-off pliers to crimp the fuel line to stop the flow.

Remove the fuel line from the fuel pump and place it in a container. Start your fuel flow.

If you find you have sufficient flow into the container, shut off the fuel flow and reattach the fuel line. Proceed with checking other fuel components for a restriction or failure.

Solution: If you do not get good fuel flow from the fuel line into the container, check any sections of fuel line or the fuel filter that could have the blockage.

Once you isolate the blockage to a specific section of fuel line, shut off your fuel flow and remove the section of line from the mower. Spray carburetor cleaner into the line to help loosen the blockage.

Follow this by blowing compressed air through the line to remove it. Repeat as necessary. If you are unable to clear the blockage, replace the line with a new fuel line.

Kubota Lawn Mower Carburetor is Dirty

The carburetor’s main purpose is to regulate the amount of fuel mixed with air to form combustion in your engine. When the carburetor doesn’t work properly, your mower can start and then die.

The carburetor becomes dirty from running old fuel that sits in your carburetor causing gummy and hard deposits to form. This can cause components on your carburetor to restrict the flow of fuel.

Solution: Before you tear your carburetor apart, make sure you are getting fuel to the carburetor. Once that is confirmed, remove your air filter and spray carburetor cleaner into the air intake.

Start your mower. If you find it dies after running, disassemble your carburetor and clean it. Follow the steps in this guide to clean your carburetor.

Plugged or Broken Cooling Fins

A Kubota mower can start and then die when the mower’s engine gets hot. Check your engine cooling fins. They may be plugged with debris or broken.

The cooling fan exists to push air around your engine block and cylinder head to keep it cool. Plugged cooling fins can restrict the amount of air circulating around your engine.

Solution: Take caution working around your hot engine. Remove any debris stuck in the cooling fins. Replace any broken fins. Clean debris around your engine and engine shroud. Ensure your heat shield is attached securely.

Insufficient Engine Oil

Your mower requires a specific amount of engine oil in the crankcase for the engine to run at its best. Most people know you can develop problems when your engine oil becomes too low, but don’t know you can also have problems if there is too much oil in the crankcase.

Too Much Engine Oil

Next, check the engine oil level in your mower. Too much engine oil in a Kubota lawn mower will cause pressure to build in the crankcase.

This can cause your mower to overheat and shut down. Read more about the impact of too much oil in a Kubota mower.

Remove some engine oil through the drain plug or oil filter. You can also use an oil evacuator or turkey baster to suck oil through the engine oil fill area. Don’t reuse the turkey baster for cooking after use.

Check the engine oil level on the dipstick. Continue to add or remove oil until the oil level is at the full line on your dipstick.

Too Little Engine Oil

You may have developed an engine oil leak or have a problem in your engine where it is using or burning oil. When you don’t have enough oil to keep the internal engine parts sufficiently lubricated, friction starts to build creating heat.

This heat can overheat your engine and cause it to die. The heat can be so hot, your internal engine parts will start to melt.

Here’s the bad news: If your engine shuts down because of a lack of engine oil, chances are significant damage was done.

Your best solution here is to take your mower to an experienced small engine mechanic to tear down your engine and perform tests to determine how much damage was done.

Bad or Dirty Spark Plug

A dirty or fouled spark plug on a Kubota mower can cause it to run sluggishly and die. Not only will a dirty plug cause this problem, but a plug that is damaged, not properly gapped, or doesn’t securely have the wires attached can cause your mower to stop running.

Solution: Clean your spark plug tip. If you find the tip of your spark plug is very dark, has a burnt electrode, or is damaged, replace your spark plug.

Make sure the plug is air-gapped following the engine manufacturer’s specifications. Securely attach your spark plug wires. Spark plugs are not very expensive. These should be replaced annually.

Bad Ignition Coil on a Kubota Mower

The winding on the Kubota ignition coil can separate and short out when the mower is hot. When this happens, the spark plugs are unable to get the voltage they need to create a spark. This can cause your mower to die after it has been running for a while.

Solution: Identify a bad ignition coil using an ohmmeter to check for a break in continuity. Replace the ignition coil if you find there is a break.

Choke is in the Wrong Position

The choke is used to start a cold engine. When the choke is engaged, air is restricted so the engine receives a higher ratio of gas to air needed to form a combustion.

Once the engine warms ups, the choke must be adjusted to allow more air so the engine continues to run. If this adjustment isn’t made, the Kubota will die after starting.

Solution: Make sure the choke lever is placed in the correct position.

Faulty Gas Cap

The fuel tank must be able to vent to keep the air pressure inside the tank equal to the atmospheric pressure. A Kubota fuel tank vents through the gas cap.

When the vent becomes plugged, the fuel tank forms a vacuum not allowing gas to flow to the engine.

To determine whether you have a bad gas cap that no longer vents, run the mower with and without the cap for periods of time to see if the mower shuts down.

If your mower shuts down with the fuel cap on and won’t start, loosen the cap to allow air inside the fuel tank and then try to start the mower again. If it starts and runs, you may have a bad fuel cap.

To further confirm the cap is the problem, tighten the cap and allow it to run again to see if the Kubota shuts off and won’t start until the cap is loosened.

Solution: Replaced a bad Kubota fuel cap.

Plugged Mower Deck

A mower deck that is plugged full of debris can cause a Kubota awn mower to shut down. This is because the engine must work harder to turn the blades through a deck full of debris. Add dull mower blades to a plugged mower deck, and it can make the problem worse.

Solution: Prevent this from happening by regularly scraping your deck to keep it clean. Sharpen the mower blades. Avoid mowing in wet conditions as wet grass clumps and sticks to your mower deck.

You can try using a deck spray to minimize grass buildup. Deck sprays are not a miracle product that prevents all buildup, it can minimize the amount of debris collecting under the deck.

Why is My Kubota Lawn Mower Battery Not Charging?

Make sure you are running your Kubota mower at a high engine speed. Don’t allow your mower to idle for long periods of time. It requires the power of the engine to charge your battery.

If you continually have to charge your battery and have confirmed the battery and wiring is in good condition and securely attached, you may have a problem with the charging system.

Solution: There are some steps you can take to check the condition of your battery and charging system which I explain in this article. If after performing these tests, you find you have a bad battery, replace your battery.

When you find the charging system isn’t working right, I highly recommend having an experienced mechanic diagnose and repair the problem.

There are so many components that can cause the charging system to fail that, unless you know the charging system, parts can be thrown at it hoping it repairs the issue.

Electrical components can get expensive and they most likely can’t be returned because they are electrical parts.