Honda lawn mower misfiring. Lawn Mower Blowing Black Smoke (Why How to Fix)

What Causes A Lawn mower Spark Plug To Turn Black? How to Clean?

Mowing a garden lawn is not an easy job, especially for new gardeners. You have most probably faced at least a single issue while using a lawnmower for maintaining this machine. You may see different types of problems in your lawnmower, and a black spark plug could be one of them.

What causes a lawn mower spark plug to turn black?

A lawnmower spark plug may turn black for several reasons, such as —

  • Long-term use of the same oil
  • Clogged air filter
  • A malfunction occurs for the carburetor
  • Selection of incorrect heat rating
  • Too old lawn mower engine
  • An inaccurate mixture of oil and fuel for 2-stroke engines

If your lawnmower spark plug has any of the above indications, it has a probability of becoming black gradually. It is best to take the precaution as early as possible before ending up damaging the spark plug.

  • What Causes A Lawn Mower Spark Plug To Turn Black?
  • Your Parts Might Be Dirty
  • Using Same Oil For A Long Time
  • Malfunction Occurs For The Carburetor
  • Selection Of Incorrect Heat Rating
  • Inaccurate Mixture of Oil And Fuel
  • Too Old Lawnmower Engine
  • Clogged Air Filter
  • Black Sooting On Spark Plugs
  • Things You Will Need
  • Step 1 —Immersing The Black Spark Plug
  • Step 2 —Keep Them For 30-40 Minutes
  • Step 3 —Take Out Spark Plug
  • Step 4 —Wash Through Running Water
  • Step 5 —Wipe Off The Spark Plug
  • Step 6 —Dry The Spark Plug
  • Excessive Fuel Consumption
  • Struggle To Run The Engine
  • Misfiring Engine
  • Unsmooth Engine Idle
  • Inspecting Visually
  • Change Oil After A Certain Time
  • Regular Cleaning
  • Take A Mechanic Help

What Causes A Lawn Mower Spark Plug To Turn Black?

What causes a lawn mower spark plug to turn black depends on several factors, which are given below:

Your Parts Might Be Dirty

Many of the engine parts become dry gradually, as such carburetor, air filter. So keeping the spark plug always clean will ensure clog-free movement.

The best course of action is to clean the spark plug regularly to prevent it from being black. You can use a regular soft brush or emery paper to clean it. Don’t forget to let the machine cool if you used it a while ago.

Using Same Oil For A Long Time

Are you using the same oil for your spark plug for a long time? Or, keeping your lawn mower idle for a long time with the old oil?

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In this case, you want to pour out the old oil from the tank and add fresh new oil. over, keeping the old oil in the tank for a long time may make the spark plug black. You may even struggle to start the engine with one attempt.

Malfunction Occurs For The Carburetor

When the ratio of air and fuel is inappropriate, imperfect combustion can result from it. The malfunction of the carburetor mainly occurs if there is an excessive amount of fuel inside the combustion chamber.

The smoke generated from this problem will be stored on the spark plug eventually. Thus, the quick black transformation of the spark plug may be associated with carburetor malfunction.

In this case, you want to configure the carburetor properly. If you don’t know how to do it, take help from the instruction manual or a mechanic.

Selection Of Incorrect Heat Rating

You always want to follow the correct heat rating for your spark plug. Following wrong heat rating not only turns the spark plug into black, but it may also damage it.

Inaccurate Mixture of Oil And Fuel

Though the latest lawn mowers have 4-stroke engines, old lawnmowers have 2-stroke engines. For a 2-stroke engine, you need to mix an exact amount of oil and fuel.

How much oil and fuel you need to mix depends on your mower model. You want to check out the instruction manual to the correct ratio.

You should avoid mixing an excessive amount of oil as it could lead to too much smoke and turn your spark plug black.

Therefore, following the correct ratio is essential to prevent this issue. However, if you don’t want to take the hassle of mixing it, you can purchase a readymade premix oil/fuel ratio.

honda, lawn, mower, misfiring, blowing

Too Old Lawnmower Engine

How many years have you used your lawnmower? Have you ever changed the engine? Many auto mechanics stated that spark plug might turn into black due to too old engine.

The old engine may not fire sparks as smoothly as it used to. Also, it may stop automatically in the middle of the mowing session.

Clogged Air Filter

Make sure the engine air filter doesn’t have any blockage issues. If the air filter in the system is clogged, it may turn the spark plug into black. If it is blocked, clean it or replace it when cleaning doesn’t eliminate the issue.

So, these are the possible reasons you want to know what causes a lawn mower spark plug to turn black. So, if you are wondering why does my lawn mower spark plug turns black, don’t take it lightly if you see any of them.

Black Sooting On Spark Plugs

The primary reason behind black sooting on spark plugs is either overheating or oil dirt. In addition, ignition systems may be negatively affected due to this.

You will notice electrodes failure due to the overheating issue. But, more importantly, spark plugs will lose the probability of recovering due because of it.

Use a new spark and see whether the new spark plug is also becoming black. If any black sooting even on the new spark plugs, the issue might be related to the cylinder or other but not with the spark plug.

How Do You Fix Black Spark Plugs?

Fixing your lawn mower spark plug is essential, and the earlier you do it, the better it is. The question of how do you fix black spark plugs depends on what is the reason behind the black issue of your spark plug. As being said, you need to implement different solutions for different reasons.

  • If your lawnmower spark plug became black due to dirt, you want to clean the spark plug to fix the issue.
  • If your lawnmower spark plug became black due to the old oil of the engine, you want to replace the oil.
  • If your lawnmower spark plug became black due to a malfunctioning carburetor, you want to fix repair the carburetor or replace it.
  • If your lawnmower spark plug became black due to an old engine, you want to replace it with a new engine.
  • If your lawnmower spark plug became black due to an inaccurate mixture of oil and fuel, you want to add the correct ratio for these two liquids.
  • If your lawnmower spark plug became black due to an incorrect heat rating, you want to follow the accurate heat rating as manufacturer instruction manuals.

You need to follow a particular solution for the type of problem your lawn mower spark plug has. Hopefully, the question of how do you fix black spark plugs has gotten cleared.

How Do You Clean Black Spark Plugs?

One of the most common solutions for black spark plugs is cleaning them properly. Even if the cause of the black spark plug is another, there is no harm in cleaning it.

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Cleaning your lawn mower spark is essential, and you want to do it regularly. According to experts, it is best to clean them for every 25 hours of use.

To cut off some efforts and, you can do it when you replace the old oil. However, the necessity arises, you should do it earlier.

Caution: Never use any hard sandpaper to clean the electrodes of the spark plug. You may end up damaging the protective coating of it. It is especially essential the protective layer is too thin.

Before knowing how you clean black spark plugs, let’s know things; you will need to clean your lawn mower spark plug.

Things You Will Need

Let’s dive into the cleaning process of black spark plugs!

Step 1 —Immersing The Black Spark Plug

First of all, make a hard detergent solution in a glass and dip the black spark plug inside the glass. Avoid immersing the insulator part, but other portions could be fully submerged.

Step 2 —Keep Them For 30-40 Minutes

You want to keep the spark plug inside the glass in this condition for 30-40 minutes. After that, you will notice a chemical cleaning reaction happens by attacking the dirt.

Step 3 —Take Out Spark Plug

After passing a reasonable time, you can now take out the spark plug from the glass solution and remove the cover too from the plug. Now, use a toothbrush or any regular brush to clean the surface gently.

Step 4 —Wash Through Running Water

After that, place the spark plug on the running water and eliminate any grease or direct build-up from the surface. Again, it could be better if the water is slightly warm for deep cleaning.

Step 5 —Wipe Off The Spark Plug

Once the washing process is done, use a soft, fresh towel to remove the remaining water from the spark plug surface.

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Step 6 —Dry The Spark Plug

The last step is drying the spark plug properly using a fan heater or hairdryer. Keep the spark plug in a clean for a few hours and then reinstall it inside the lawnmower.

So, now you know the question of how to do you clean black spark plugs. Make sure you follow the steps carefully to keep it damage-free. In addition, cleaning your spark plug will improve the engine performance by up to 10-15%.

How Can You Tell When A Spark Plug Is Bad?

A bad spark plug doesn’t allow you to run your mower smoothly and efficiently. But the question is, how can you tell when a spark plug is bad? Here are the most common indications you will see on a bad spark plug:

Excessive Fuel Consumption

Your lawn mower engine will consume more fuel than earlier when a spark plug becomes foul or bad.

Struggle To Run The Engine

Are you struggling to run the mower engine even after trying several times? You may think it is because the battery is dead or no oil in the tank. But it can be associated with a bad spark plug. Unless the engine generates enough sparks, you can’t start the lawnmower.

Misfiring Engine

A faulty spark plug may prevent you from running the lawnmower consistently. It may stop in the middle of the lawn cutting and disrupt the cutting process.

Unsmooth Engine Idle

Have you noticed any abnormal sound from the engine? It is supposed to operate steadily and consistently with typical sound. But, from a foul spark plug, you may notice rattling noises or even vibrations is coming.

Inspecting Visually

If you have a new spark plug at home, compare the new one with the old one and notice the difference. If the electrode or tip appears to be excessively worn, you want to replace it.

Can I Clean And Reuse Spark Plugs?

Are you facing any issues with your lawnmower spark plug? Are you wondering whether you can use it after cleaning or you must replace it?

Can I clean and reuse spark plugs?

Whether you can use your old spark plug or not after cleaning depends on its conditions and the type of spark plug you have. If your lawnmower has a platinum or iridium plug, you may reuse it after cleaning. But it should be free from physical damage or other issues.

If the spark plug is bad or faulty, cleaning it may not allow you to reuse it. Check the signs of bad or faulty sparks, which we have mentioned. So the question of can clean and reuse spark plugs relies on your spark plug physical condition.

Can You Clean A Spark Plug With WD40?

Do you think WD40 is only intended to serve as a squeak-removing agent for various objects? The multi-purpose nature of WD40 often stuns us with its surprising uses.

Can you clean a spark plug with WD40? YES! You surely can—using it correctly is all that is needed.

How To Clean A Lawnmower Spark Plug With WD40?

Cleaning the spark plug with an effective cleaning agent will remove unwanted dirt and grease from the surface and allows you to perform better. Here are the procedures:

  • First of all, let the lawnmower engine cool down if you have used it recently.
  • Remove the plug from the lawnmower and keep it aside.
  • Then, take a new fabric and apply the WD40 solution to the fabric by spraying.
  • Now, gently rub the fabric on the spark plug surface. Avoid overdoing it.
  • Let it dry. Then, reinstall it. See the difference!

That’s the step you want to follow when you want to know the question of can you clean a spark plug with WD40.

What Is The Best Way To Stop A Black Spark Plug?

You have already known what causes a lawn mower spark plug to turn black. To keep the plug from turning black again, you want to know how to maintain it.

You are not someone who will waste money buying a new spark plug unnecessarily. Here are the following factors that can help you prevent blackening the spark plug:

Lawn mower smoking? Reasons why and how to fix it!

Change Oil After A Certain Time

Using the same oil for a long time may make the spark plug prone to be black. This is because old oil may enter into to system and make the plug black. Additionally, new oil prevents damage to the engine and carburetor.

Regular Cleaning

Regular cleaning is essential for any engine components, and so does for the spark plug. However, you don’t need to take the hassle of cleaning the spark plug after every cutting season. It will be best to clean the lawn mower spark plug once or twice each year.

Take A Mechanic Help

If you still see the black issue on the spark plug even after cleaning and regular oil change, take a professional mechanic to help to deal with the issue.

What Is The Recommended Interval For Replacing A Spark Plug?

You have figured out what causes a lawn mower spark plug to turn black, but you are still uncertain whether you should replace the spark plug or not.

The best-recommended interval for replacing a spark plug is around 100 hours of usage. Or, you can replace the spark plug after every season. When the engine sits idle for a long time at the end of the season, it may not work as perfectly as it did.

Replacing the lawnmower after every season or 100 hours of usage will reduce excessive fuel consumption and unwanted operating issues.

Therefore, you want to maintain and replace this vital component regularly to ensure efficiency.

Keep Your Lawnmower Spark Plug Always Inspected!

It is common to encounter problem machine parts. Whenever you notice any abnormality on the spark plug, you should always check them out.

As you are already the question of why does my lawn mower spark plug turn black, you can tell what problem your spark plug has. Most importantly, check out the physical appearance, whether it has any worn-out issue or not.

Final Thought

Knowing what causes a lawn mower spark plug to turn black can help you to make an informed decision. Also, you can decide whether you should replace it or just clean it will solve the problem. So, don’t forget to take care of your lawnmower appropriately to ensure engine efficiency.

Last update on 2023-01-28 / Affiliate links / Images from Amazon Product Advertising API

Lee Safin was born near Sacramento, California on a prune growing farm. His parents were immigrants from Russia who had fled the Bolshevik Revolution. They were determined to give their children a better life than they had known. Education was the key for Lee and his siblings, so they could make their own way in the world. Lee attended five universities, where he studied plant sciences and soil technologies. He also has many years of experience in the U.S. Department of Agriculture as a commercial fertilizer formulator.

Thoughts on What Causes A Lawn mower Spark Plug To Turn Black? How to Clean?

Lawn Mower Blowing Black Smoke (Why How to Fix)

If you’re out cutting the grass, the last thing you want is to send up a smoke signal letting everybody know that something is wrong with your lawn mower. Still, you can’t always prevent it. Smoke coming from your lawn mower is a telltale sign that something is going (or has gone) wrong. Mowers can produce either white/bluish smoke or black smoke. If your lawn mower is blowing black smoke, there are usually just a few major reasons for it.

Why is My Lawn Mower Blowing Black Smoke?

A lawn mower blowing black smoke means that the engine is running rich and is usually caused by the choke set/stuck “on”, a blocked air filter, or a carburetor that isn’t working correctly. Combustion engines depend on a mixture of fuel and air, and when there is too much fuel in the mix, it is considered rich (when there is too little fuel in the mixture it is considered lean).

Let’s take a look at each reason why your engine could be getting a rich mixture resulting in your lawn mower blowing black smoke.

Choke Set or Stuck “On”

Lawn mowers use either a choke or primer bulb to help get them started when the engine is cold. The choke on your lawn mower is used to enrich the gas and air mixture that the engine gets when first starting the mower. It’s called choking because the fuel/air mix is enriched by restricting the amount of air that can enter the carburetor. A primer bulb enriches the fuel/air mix by pushing extra fuel into the engine. Once the engine is running or warmed up a bit, the choke should be turned off. If it isn’t turned off, or it gets stuck on, the rich fuel and air mix will produce black smoke.

Only manual and automatic chokes can cause black smoke, primer bulbs will not. Double-check that your choke setting isn’t the issue first. If it isn’t, then run the mower and see if changing the choke settings affect how the lawn mower runs. If the choke seems to be working correctly, you’ll have to look into the air filter or carburetor.

Blocked Air Filter

Your mower’s air filter is super important and something that should be checked and cleaned off a couple of times a season. Technically it’s recommended that you clean your air filter every 25 hours of operation, and replace it every 100 hours. If your air filter is overly dirty or wet it can block air from getting to the engine. This is another way that you can end up with a rich fuel and air mixture creating black smoke. Luckily, it’s pretty easy to get at your air filter on most lawn mowers.

To tell if this is your problem, take a look at the air filter and if it has a bunch of dust or debris on it, try and clean it off. If it is wet or oily you should probably replace it. Then, once you have your cleaned or new air filter reinstalled, run the mower and see if the black smoke clears. Some people recommend taking the filter off and running the mower without an air filter to see if it’s the problem, but I wouldn’t advise doing that. It’s an easy way to suck a bunch of gunk into your carburetor or engine.

Carburetor Problems

This usually isn’t the case but if you know that your choke and air filter are working correctly, the cause of your black smoke is probably due to the carburetor not working properly. The job of the carburetor is to mix fuel and air and shoot it into the engine. If the fuel and air aren’t being combined in the right ratio, the engine won’t run as it should. In the case of black smoke, the carburetor isn’t supplying enough air.

How to Fix a Lawn Mower Blowing Black Smoke

Fixing a lawn mower blowing black smoke means bringing the air and fuel mixture that the engine burns back into balance. Each of the three causes of a rich fuel mix has a different fix, so let’s check them out.

Choke Set or Stuck “On”

If your lawn mower has a manual (lever) choke, fixing the choke may be as simple as turning the choke off when the mower is running. But if that doesn’t work, or you have an automatic choke, you’ll need to dig a bit deeper.

Manual Choke:

Adjust the choke when the mower is running to see if it changes how the engine runs. Turning the choke off should make the engine run smoothly (and without black smoke) and leaving the choke on should cause the engine to run roughly. If the choke doesn’t seem to work as it should, you will have to adjust the cables that control the choke flap opening and closing. This isn’t a super complicated job but usually requires the removal of the carburetor.

Automatic Choke:

If you have a newer lawn mower, it could have an automatic choke. These adjust themselves using a thermometer reading. As the engine warms, the thermometer should force the choke flap to open (turning it off). If it isn’t working properly it is usually because the thermometer is broken, or the links attached to the choke flap aren’t allowing it to open and close. Replacing these parts can be a bit more tricky than dealing with a manual choke.

Blocked Air Filter

Cleaning off your filter can be done relatively easily. Usually, there is just a plastic clip or a set of wingnuts or small bolts holding the filter in place. Blowing off the air filter with compressed air, or tapping it down on a clean surface will usually shake off any loose dirt or debris.

But if the filter has gotten wet or soaked up any oil, you’ll need to replace it. The part isn’t expensive, and installing a new filter just requires reversing the steps you take to remove it. It’s worth maintaining a clean air filter because it will help your mower in more ways than one.

Carburetor Problems

Again, if the choke is turned off, and the air filter is clean, the carburetor is now your prime suspect. Fixing a carburetor that is mixing too much air in means two things: adjusting the airscrews, or replacing the carburetor. The airscrews on carburetors are always screwed in a precise amount to control the air intake. You’ll need to reference a service manual or manufacturer’s specifications to determine how far the screw should be set. Usually, you need to turn the screw all the way and then back it out a set number of turns.

If you go through the trouble of removing the carburetor and find that the screw was already set correctly, you will have to replace the carburetor. Depending on what type of lawn mower you have, it shouldn’t be too costly to do yourself. If you don’t have the tools or know-how to tear into your carburetor, you should have a small engine mechanic tackle the project for you.

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Why is My Riding Lawn Mower Blowing Black Smoke?

Riding lawn mowers blowing black smoke do so for the exact same reason that push mowers do: a rich fuel and air mixture. Check the choke, and air filter first to see that they are functioning as they should. If they are, you will have to check for carburetor malfunctions.

Causes of 4 Stroke Lawn Mower Blowing Black Smoke

Unlike a lawn mower blowing white or blue smoke, 4-stroke and 2-stroke mowers blow black smoke for the same reasons. The type of choke is essentially the only thing that will differ between push mowers. Again, if your mower has a primer bulb, the choke is not the issue and you’ll need to look at the air filter or carburetor.

Causes of 2 Stroke Lawn Mower Blowing Black Smoke

As I mentioned in the section above, a 2-stroke mower will blow black smoke for the same reason as a 4-stroke mower. Because black smoke is related to the fuel and air mixture, all lawn mowers produce black smoke for the same reasons. But, to be clear, this isn’t always the case for white or blue smoke.

Is Black Smoke from Lawn Mower Dangerous?

Black smoke from a lawn mower isn’t only bad to look at, it can actually be dangerous for a number of reasons. First off, black smoke is basically just soot from unburned gas/fuel being pushed out through the exhaust. If inhaling gas fumes is bad for you, you definitely don’t want to breathe in a bunch of sooty fuel that has run through your engine. Also, black smoke coming from your lawn mower can signal damage occurring within the mower. A lawn mower burning a rich fuel/air mixture can lead to you needing to replace choke parts, an air filter, spark plugs, or even the carburetor itself. If you see black smoke, be sure to address the problem right away.

About Tom Greene

I’ve always had a keen interest in lawn care as long as I can remember. Friends used to call me the lawn mower guru (hence the site name), but I’m anything but. I just enjoy cutting my lawn and spending time outdoors. I also love the well-deserved doughnuts and coffee afterward!

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Lawn Mower Smoking and Sputtering- How to Fix [DIY Solution]

Have you ever experienced that your mower is smoking black or white? It’s truly an embarrassing situation for all who just started their lawn mowing but stopped due to smoking and sputtering. If you want to fix the problem, you first need to know why the lawn mower is smoking and sputtering.

Smoking and sputtering can occur in a lawn mower due to some possible reasons. It may happen due to incomplete combustion, overfilling the lawn mower with excessive oil, tipping it the wrong way, and inflating the gasket.

Don’t worry; if you find such problems in your lawn machine that can cause smoking and sputtering, you can fix them yourself. Let’s dive into the topic.

Reasons Why You Lawn Mower Smoking and Sputtering

Your lawn mower is misfiring, putting out black smoke? Let’s know the key reasons below.

Overfill With Engine Oil:

Like a car, you shouldn’t overfill your lawnmower with excessive engine oil because it can overheat the engine.

Your engine might get locked up due to excessive engine oil in your lawn mower. In that case, the engine will not run well and cause smoke. It is one of the most common things that you may come across.

Note: You will face the sputtering problem in your lawn mower due to using old or wrong fuel.

Tip: Check the air filter to ensure it isn’t overfilled with oil. You can use the dipstick to check the oil level.

Tip Over the Lawn Mower in the Wrong Way:

Another common reason for lawn mower smoking and sputtering is tip over the lawn mower incorrectly. If you tip the mower the wrong way, the chances are that the oil will leak into the tube and restrict the fuel line.

Or, if the oil moves into the breathing tube, oil can restrict the air filter. Thus the engine can’t run and cause the problem.

Tip: You can replace the faulty tube with a new one or replace the air filter.

Inflated Gasket:

If the gasket gets a little crack, it will start leaking out the oil, clogging the fuel line and restricting the engine’s running. Ultimately, the engine will be overheated and cause smoking.

Tip: You can repair the gasket crack or change the faulty one with a new head gasket.

Incomplete Combustion:

It happens because of incomplete combustion. Generally, sputtering or smoking is caused by two things.

  • The first one is your spark plug either fouling or not working properly. There is no appropriate gapping.
  • The second reason can be the air filter when it is dirty and not working properly. It can cause incomplete combustion.

Basically, the reason why it causes incomplete combustion (when the spark plug or filter is not working properly) is because of the fuel. The fuel is coming through the lawnmower, but it is not properly burning.

Because of the incomplete fuel burning, it blows out black smoke; your lawnmower will run roughly. You may also experience your lawn mower losing power or backfiring etc.

How to Troubleshoot the Lawn Mower Smoking and Sputtering? Easy 2 Methods

To sort out the problem, the first thing that you usually check is to check the air filter. You should ensure that it is clean and clear, and after that, you must check the spark plug.

Inspect if the plug is really black or carbonated. You may need to change the plug or clean it. Also, inspect the gap and ensure that there is an appropriate one on the spot.

Here, I will explain the process of checking and cleaning the air filter and then the Spark plug. So, let’s come to the diagnosis process.

Step 1- Check the Airport

First of all, you should check the airport. It is all nice. Ensure it should be clean enough. Unscrew the screws and tap the box to open the airport.

Step 2- Inspect the Airport

Once you have removed the airport, inspect it thoroughly. Make sure there should be no dust in excessive amounts.

Step 3- Take off the Foam

For proper cleanliness, take out the foam from the filter and check it thoroughly.

You can see old lawn clippings, dust, and everything like that. Such hurdles add to misfiring and incomplete combustion.

It is a non-effective air filter that deteriorates the overall performance. So you need to clean it. Clean it thoroughly and ensure all the debris and grass particles are removed.

Once it is properly cleaned, reinstall it at the previous place. Check the lawnmower; if it is still sputtering or smoking, then the problem is with the spark plug so check for the spark plug.

Method 2: Check and Fix the Lawnmower Spark Plug?

Here I will teach you three simple steps to check clean and then replace the spark plug if needed. It will boost the engine performance.

Things You Will Need:

  • Spark Plug Wrench
  • Hex turning tool
  • Spark plug wire brush
  • Spark plug gapping tool

Step 1- Read the Manual

It will help you to finish your job quickly and perfectly if you read the instruction manual.

Step 2- Check for Spark Plug

First, you must remove the spark plug to check it thoroughly.

Start with removing the spark plug wire. You can grip it and go ahead and pull it straight off of the spark plug.

Then move it out of the way, get a spark plug wrench, and place it over the spark plug until you feel it engaged.

Then install the hex turning tool and loosen the spark plug. You may need to turn it on for a few seconds.

Once it is removed, you can inspect the spark plug. You can see it is dark and covered with carbon. You can restore it after cleaning the carbon. Also, check for the gap.

Step 3- Clean the Spark Plug

Take a soft wire brush; it would protect your spark plug from damage.

While cleaning it with a brush, start from the outside edge of the spark plug and then turn it. You will be able to access the entire surface and also check for the spark plug gap.

That looks fairly good now; check for the spark plug gap. You should use the spark plug gapping tool.

Insert the tool between the open and gap in the spark plug on the smallest end; this is point zero to zero.

Then slide the spark plug up until it stops. Check the measurement; it should be less than zero

Reinstall it, but if needed replacement, go ahead to replace it with a new one.

Step 4- Replace the Spark Plug

Take a brand new Spark plug that should be compatible with your engine brand. Then take a spark plug wrench to remove the older one and install a newer spark plug.

Place the new spark plug at the end of the wrench and carefully turn the spark plug. Turn it until you feel the threat set, and keep it turning slowly until the spark plug stops.

Tighten it some more to ensure correct installation.

Once you have tightened it, finally reattach the spark plug wire.

Switch on the lawnmower to test, hope there will be no sputtering or smoking issue. You have done your job well.

Frequently Asked Questions(FAQs):

What are signs that a lawn mower air filter is bad?

You may notice poor engine performance if there is a problem with the air filter. Common signs include hard starting, random misfire or sputtering, stalling, smoking, and failure of fuel system parts.

What does it mean when my lawn mower smokes grey or blue?

If you notice your lawn mower is smoking blue or grey smoke, it means the problem is with the engine. Your engine is burning the fuel inside the combustion chamber. Maybe there is leakage of valve seals or bad piston rings.

There may be an issue with the combustion chamber. Coolant or water is vaporized in the combustion chamber, producing white smoke.

What happens if my lawnmower is sputtering or smoking?

If your lawnmower smokes, there is no harm except an unpleasant mowing experience. It may cause frequent engine stalling if you do not immediately remove the issue.

Final Verdict

Lawnmower smoking or sputtering is a common issue you can fix in a couple of minutes. Air filters, combustion chamber, spark plugs, fuel quality, and poor wiring can be possible reasons for smoking.

You should immediately identify and fix the issue for a smooth mowing experience. If you find it tough to solve the problem, then please don’t hesitate to take professional help.


Quick Guide for GX120, GX160, GX200: Honda Small Engines Troubleshooting

A good cross-skill for any tradie is the ability to troubleshoot equipment on the job.

Some repairs require a professional mechanic. Other repairs are more straightforward; you can do them yourself. This article focuses on basic small engine troubleshooting, in particular, for the four stroke GX120, the GX160, and the GX200 Honda small engines.

About the GX120, the GX160 and the GX200 Honda Small Engines

In 2011, Honda launched an updated version of its 4 stroke GX engines line. The GX120, GX160, and GX200 are horizontal-shaft, single-cylinder engines that replaced the existing models.

The engines’ designs are for turf and commercial applications and related equipment. Examples are construction and industrial equipment, generators, and agricultural equipment. They are also suitable for pressure washers and water pumps.

The GX series engines have appealing features such as good fuel economy and lower noise levels. They have a reputation for their fuel economy as well as durability and reliability.

Honda Small Engines Troubleshooting

Below are some fundamental Honda troubleshooting issues and their probable causes for the GX120, the GX160 and the GX200 Honda Engines. Keep in mind these are broad small engine troubleshooting tips.

For detailed mower troubleshooting, generator troubleshooting, etc., refer to the Honda small engine manuals for each engine.

Engine Won’t Start, Won’t Stay Running, Runs Poorly, or Is Hard to Start

For these engine issues, the probable causes appear below, beginning with the most common cause.

Check the Fuel

It might sound obvious, but it has to be said. If your engine does not start, the most obvious thing to check is that it has not run out of petrol. Make sure that you are using straight petrol for a 4 stroke engine.

Also consider the age of the fuel, if it has been more than 3 months it may have gone stale. It is extremely hard to start a machine with stale fuel.


If your engine won’t start, starts but stops after a few seconds, the carburetor may be the cause. When you leave fuel in the engine for an extended period, you can clog the carburetor. After some time, parts within the fuel evaporate.

They leave a sticky substance behind that clogs up the carburetor. Clean it with carburetor cleaner and if that doesn’t work, you will have to replace or rebuild the carburetor.

Where you find it hard to start the engine, your engine may be getting too much or not enough fuel.

If your carburetor is clogged, the engine doesn’t get the fuel it needs. The engine receives too much fuel if the carburetor choke isn’t closing as it should.

Fuel Cap

A clogged carburetor is usually the culprit when the engine stops after running a few seconds or more. Another common cause is a faulty fuel cap. A faulty cap keeps the engine from starting or makes it harder to start the engine.

As the engine consumes fuel, pressure rises in the gas tank. The gas cap has a small vent that allows air to enter the gas tank and relieve pressure. If that vent becomes clogged, the pressure in the tank will rise.

When the gas tank pressure exceeds the engine pressure, the engine stalls. Loosen the gas cap before you start the engine. If the engine continues to run with the loose cap, the vent is more than likely clogged.

Spark Plug

Check the spark plug for damage or wear. You may see a cracked insulator, a burned-away or damaged electrode, or heavy carbon buildup. If so, replace the spark plug.

You can also use a spark plug tester to see if the spark plug is defective. You should see a strong spark between the tester’s terminals when the engine is cranking. If you don’t, the spark plug is defective.

Fuel Filter

A clogged fuel filter can cause engine problems. If someone leaves fuel in the engine for a long time, some of the fuel’s ingredients evaporate. The sticky stuff left behind clogs the fuel filter and interferes with engine operation.

If you find old fuel in the engine, drain it from the fuel tank. Then, replace the fuel filter.

Ignition Coil

While the engine is running, the ignition coil sends volts to the spark plug. A faulty ignition coil keeps the engine from starting. Check that the spark plug is working.

If it is, use an ignition coil tester to test the ignition coil. Replace the ignition coil if needed.

Recoil Starter

The recoil starter engages the crankshaft, which turns over the engine. If the recoil starter assembly is faulty, your engine will not start. To troubleshoot, remover the starter assembly.

Check that it’s working. Pull the starter rope.

The tabs that extend from the pulley and cam should catch the engine hub. This turns the engine. Release the rope. The tabs are supposed to retract. Then the rope should rewind on the pulley.

Start Switch

A faulty start switch will keep the engine from starting. To see if the switch is defective, use a multimeter. Test for continuity.

Also, the switch should have one open contact, which is the ‘on’ position. It will also have one closed contact in the ‘off’ position.

If you have trouble turning the switch, or if the switch only works part of the time, replace it.

Safety Switch and On/Off Switch

Like the start switch, you can test both the multimeter of these switches to see if they are defective. Either one can prevent the engine from starting if it’s faulty.

Flywheel Key

The flywheel key is a small, metal piece. It fits in the crankshaft, where it engages with the flywheel.

If the engine suddenly stops, the flywheel key will break in half. This prevents engine damage. Replace the flywheel key before troubleshooting further.

Maintaining Your Small Engine and other Equipment

Sometimes, small engine troubleshooting is something you can handle yourself. Maintaining your equipment yourself can save you a great deal of time and money.

Of course, there are times when a mechanic is needed, especially when your income depends on it. That where we come in. Here at Canberra Diamond Blade Suppliers, we service, repair and sell construction and garden machinery and replacement engines right here in our local workshop in Canberra, ACT.

If the help we have given you today on troubleshooting small engines is not enough, it may be time to bring your machine in for us to take a look. We know that the last thing you want is to be loosing time and money because of sick machinery. Don’t hesitate to contact us on 02 6242 8996 if you want us to look at your engine.

Did you know that we have an online store, and we sell tools, machines and PPE? We are also a face mask supplier, so if you don’t know where to get one, we can help you out.