Any type of smoke coming from your Honda mower can be alarming and a cause for concern. The last thing you want to happen is ruin the engine further by continuing to run the mower, so you stop to find the cause of the smoking.
A Honda lawn mower may begin smoking from an air restriction caused by a plugged air filter; an inefficient engine oil level; a leak in the engine; or an internal engine problem resulting from a piston ring or valve train problem.
While you may be lucky and be able to find and fix your smoking problem before it causes significant problems, a smoking mower may indicate a larger internal engine problem.
This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.
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 Your Honda Lawn Mower is Smoking
Air Filter is Plugged
Your mower requires a clean air filter to allow air to pass through it and to the engine. When the filter becomes plugged, it can cause your Honda mower to smoke and possibly cause engine damage. Here are a few things that can result from a plugged air filter:
- The lack of air in the engine will cause your Honda mower to run rich and emit black smoke. Running rich is when your engine is receiving a higher concentration of fuel-to-air mixture than required.
- When the filter is so plugged the engine is unable to draw air through the air filter, it will begin looking for air anywhere it can find it. This can include drawing air from the crankcase. When this happens, oil can also be pulled with the air creating smoke when it burns off in the cylinder.
- Smoke created in the engine can cause your air filter to become plugged further magnifying your smoking problem.
It is important to always use an air filter in your Honda mower. Not doing so can cause significant damage. Not only should you be using an air filter, you need to use a clean air filter. It is good practice to replace your air filter once a year during your annually routine maintenance.
Then, regularly check and clean your air filter throughout the mowing season. Checking, cleaning, and replacing your air filter regularly is an inexpensive maintenance item to prevent a costly engine repair.
Clean your Honda mower paper air filter by removing it from the air filter housing. Wipe out any dirt remaining in your housing being careful not to knock dirt into the air intake. Tap your air filter against a solid surface to knock as much dirt as possible.
If you can see light through your air filter when holding it up to a light source, go ahead and reuse it. If not, replace it with a new air filter. Reinstall your filter and the air filter housing cover.
Have a foam air filter? Find cleaning instructions here.
Engine Oil Level is Too Low
Good engine oil is required to lubricate the moving parts in your engine. Your Honda mower requires a specific amount of engine oil to be used in the crankcase. When your engine oil is too low, the parts are no longer sufficiently lubricated.
Friction begins to build from the moving parts creating heat. This heat can be so hot, it begins to melt internal engine parts and oil begins to burn off creating smoke.
Because of the damage a low engine oil level can cause to your engine, it is necessary to check your engine oil level before each use of your Honda mower.
Checking the oil level can identify signs of an oil leak or alert you to problems at an early stage where the mower is consuming or burning oil. When a low level isn’t caught soon enough and smoking occurs, it is often too late to solve with a quick fix such as adding more engine oil.
Smoking due to low engine oil often means you have a significant engine problem that will need to be diagnosed by a small engine mechanic.
Engine Oil Level is Too High
Most people are aware that it is not good to run your engine with a low engine oil level, but they don’t always know running your Honda mower with too much engine oil can also be a problem.
Too much engine oil can increase the pressure in your crankcase which can push oil into the cylinder and even up to the air intake through the valve train.
The oil in the cylinder can begin to burn off and smoke. Read more about other results of running your Honda mower with too much oil in my article here.
Remove excess engine oil until the level registers within the full lines on your engine oil dipstick. You can easily remove a little oil through a drain plug, but I prefer using an oil evacuator or a turkey baster. (Yes, like the one in your kitchen).
Bad Engine Gasket
You may experience an engine oil leak that can drip onto the muffler and cause your Honda mower to begin to smoke. Inspect your engine to find the oil leak and repair the problem. An oil leak is often the result of a bad gasket on your engine.
Piston Ring Problem
Now that you have checked out all the items you can identify by inspecting some parts and checking engine oil levels, it is hard to clearly identify additional causes of smoking.
This is because the other problems are internal engine problems. You will have to tear down the engine and run tests to identify the problem.
While you can’t isolate an internal engine problem without tearing it down, you can check your spark plugs for signs of oil on the tips.
This will point to an internal engine problem, but won’t pinpoint the exact problem. When you find oil on the spark plug, it may be an indication of a piston ring or valve train problem.
The engine will have to be torn down. A piston ring problem or scoring inside the cylinder wall may be found. This causes oil to enter the combustion chamber and burn off.
Valve Train Problem
Another internal problem that can develop in your Honda mower is the valve train. You can develop a burnt valve when the valve has overheated. A red hot muffler can be a sign of a burnt valve or timing problem.
The only way to determine a burnt valve problem is by removing the cylinder head and performing a leak-down test.
If a burnt valve is found, the valve and seat will have to be cut at certain angles to complete the combustion chamber. Bring your Honda mower to a small engine mechanic to have this work performed.
Honda Lawn Mower is Emitting Blue, White, or Black Smoke. What’s the Difference?
While I recommend using the steps above to identify your smoking problem, the color of the smoke can indicate the type of problem you are having with your Honda mower.
Blue or White Smoke is associated with the burning of excess oil. This could be from oil burning off in the combustion chamber from damaged piston rings, valve train, or engine gasket leaks.
It can also be the cause of oil being pushed into the cylinder from a plugged air filter.
Black Smoke is associated with excess fuel burning. This is due to a plugged air filter allowing the ratio of fuel to air to have a higher fuel concentration.
When the Honda mower runs rich, it can emit black smoke. If the air filter is not the cause, look for another air restriction in the mower.