Smoke is rolling out of your Kubota mower. You immediately get deflated thinking you have a large repair bill ahead of you. While smoke coming from your mower is never a good thing, sometimes if the cause of the smoke is caught early, you may be able to correct the problem without spending a lot of money.

There are other times when the sign of smoke indicates significant engine damage that could result in needing repairs or an engine replacement.

A Kubota lawn mower may be smoking from a lack of air due to a clogged air filter or stuck choke; an insufficient engine oil level; a bad engine gasket in your mower; or a problem with the piston ring or valve train.

Performing routine maintenance on your Kubota mower can help you spot early signs of problems developing in your mower. Checking the mower over before each mowing, including checking the engine oil level and air filter can prevent significant damage to the engine.

Kubota lawn mower is smoking

6 Reasons Why Your Kubota Lawn Mower is Smoking

Kubota Air Filter is Plugged

Your Kubota mower requires clean air to keep the engine running. When it is unable to get sufficient airflow because the air filter is plugged, it can begin to run rich and emit black smoke. Running rich is when the ratio of fuel to air has a higher fuel content and lower air content.

Smoke can also be caused when the air filter becomes so plugged the engine isn’t able to pull air through the air intake. It will look for air wherever it can find it.

This may result in pulling air from the engine crankcase. Oil can be pulled into the cylinder with the air. When this oil burns off, it will create smoke.

Clean air is essential to keeping your Kubota lawn mower running at its best. A clogged air filter can cause your mower to overheat and cause possible internal engine damage.

I recommend replacing your air filter annually during your annual Kubota maintenance.

Then, check and clean your air filter several times during the mowing season. Check it more often when you are mowing in dry dusty conditions. Never run your mower without an air filter. Dirt and debris in the engine can cause significant damage.

Steps to clean your Kubota lawn mower air filter

  • Remove the paper air filter element from your air filter housing.
  • Wipe out any dirt remaining in the air filter housing with a dry clean rag. Don’t allow any dirt to enter the air intake.
  • Tap your air filter against a hard surface to knock as much dirt loose as possible.
  • Once no more dirt falls from your air filter, hold the filter up to a light source.
  • If you see light shine through the paper filter, it is okay to continue using it.
  • If you don’t see light through the paper element, replace it with a new air filter.
  • Replace the air filter and secure the air filter housing cover.

Low Engine Oil Level in Your Kubota Mower

When your engine crankcase doesn’t have enough oil in it to properly lubricate your internal engine components, friction can build among the moving parts.

This increased friction can build heat and become so hot the components can start to melt and the oil can begin to burn off creating smoke. You can try to correct the issue by correcting your oil level, but it most likely won’t help.

When you get in a situation where low oil has caused your engine to start smoking, there is a good chance you have caused significant engine damage that can result in a large repair bill or even an engine replacement.

It is necessary, not just a suggestion, to check your engine oil level before each mowing. By doing this, you can catch problems during the early stages. A low engine oil level can point to an oil leak or indicate your mower is burning or consuming oil.

When you experience a low engine oil level, check over your engine for oil leaks and repair. If you can’t find the reason for your low oil level, have an experienced small engine mechanic check out your engine.

The mechanic can perform some tests to identify the problem before you do any additional damage by running your Kubota lawn mower.

Too Much Engine Oil in Your Kubota Mower

Having too much oil in your engine can cause pressure to build in the crankcase. This pressure will push oil into your cylinder and up into the air intake through the valve train. Smoke is created when the oil burns off in the cylinder.

The smoke can plug your air filter. The filter can also become covered with oil when oil is pushed through the air intake. Replace your air filter when you find signs of oil or it has become plugged.

Correct your engine oil level bringing it to your manufacturer’s required level. You should find a couple of lines on your oil dipstick that indicates the full level of your engine oil.

Remove oil by draining a little oil from your Kubota’s drain plug or oil filter. You can also use an evacuator or turkey baster to suck a little oil from the oil fill area.

Recheck your engine oil level and continue to drain or add a little oil until you are at the full level…no higher and no lower.

Bad Engine Gasket in Your Kubota Mower

A bad gasket in your engine can cause oil to leak. When oil leaks onto your muffler, it will begin to smoke once it burns off. Inspect your engine for leaks, and replace the gasket that is causing the leak.

This can be a pretty easy fix. It can become increasingly difficult depending on the placement of the failed gasket.

Piston Ring Problem in Your Kubota Mower’s Engine

If any of the prior items is not your problem, it can be more difficult to determine the exact cause of your Kubota’s smoking issue because it is likely to be an internal engine problem that will take a small engine mechanic to tear down your engine and perform tests to identify the cause.

While you can’t clearly identify the exact cause of an internal issue without performing these tests, you can check your spark plug for oil. This will indicate you have an internal engine problem and it’s time to have your engine checked out.

Remove your spark plug using a 3/4” or 5/8” socket (varies by engine model) and check the tip of the plug for signs of oil. Oil on the plug can indicate you have a piston ring or valve train problem.

When you find oil on your spark plug, a mechanic will need to tear down your engine.

The mechanic may find scoring on the cylinder wall that is allowing oil to enter the combustion chamber and burn off creating smoke. Oil could also be leaking past a failed piston ring. A compression test can help identify the problem.

Valve Train Problem in Your Kubota Mower’s Engine

Your Kubota mower may smoke from a burnt valve in your engine. A burnt valve is one that has been overheated.

While a red-hot muffler can indicate a burnt valve or timing problem, the only way to clearly identify a burnt valve problem is by removing the cylinder head and performing a leak-down test.

This test should be performed by an experienced small engine mechanic. When a burnt valve is found, the mechanic is required to cut the valve and seat it at specific angles to seat it correctly. It is necessary to get this repair correct. This will complete the engine combustion chamber.

Difference Between Black, White and Blue Smoke Coming from Your Kubota Lawn Mower

The color of the smoke can indicate what type of problem you have. It shouldn’t be a replacement for the steps above. Instead, the information should be used together to identify your Kubota mower’s smoking problem.

White or Blue Smoke: This color of smoke is formed when excess oil is burning off. Follow the steps above to identify the root cause.

Check for oil leaking on your muffler, a plugged air filter, and the engine oil level. Follow this by determining whether you have an internal engine problem.

Black Smoke: This is often caused by your Kubota mower running rich, burning a higher concentration of required fuel than air. Check for a plugged air filter preventing air to get to your engine. If this is not your problem, look for other airflow restrictions including a stuck choke.

Still Experiencing Problems with your Kubota Lawn Mower?

Own a lawn mower long enough, you’ll start running into problems with it starting, not continuing to run, smoking, leaking gas, giving a bad cut, vibrating, or another issue.

To help you save time and money, I have put together a guide to help you troubleshoot the next problem that develops on your Kubota mower.

You can find this guide at Common Kubota Lawn Mower Problems & Solutions.

If you are unsure how to perform diagnostics and repairs on your Kubota lawn mower safely, it’s best to have a professional complete the repairs.

This will help you avoid personal injury or additional damage to the mower. Your local Kubota lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.

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