Is your lawnmower smoking and scared the pants off of you? Don’t be alarmed. You have a right to be afraid, and it is warranted.
You might be wondering why would a lawnmower blow white smoke anyway? Is it part of its whole functionality?
There can be many reasons why a typical mower will discharge smoke, and a lot of them do not necessitate the aid of a service technician.
A knowledgeable homeowner can detect the reason for a smoke-emitting mower by judging its color coming out of the engine and fixing it accordingly. You have to remember that all internal combustion engines have the same components. But due to their different make and model, the configurations vary from each other.
Table of Contents
Why is your lawn mower smoking?
In most situations, a particular mower will suddenly expel either white or blue smoke. It’s due to oil spilling out onto the engine. Perhaps you’ve changed its oil or topped it off or overfilling it. Or maybe you have turned it upside down or on its side for maintenance purposes.
Even the act of mowing in a very inclined slope can be the reason. A conventional gas-powered mower’s lubricating system cannot be properly sealed. And what can happen is that the oil reserve will overflow to the relief outlet where extra oil is leaked into.
Different kinds of smoke
To get the best engine smoke treatment, you must distinguish the various smoke colors issuing forth from the engine. This way, you can diagnose the problem.
After ten to fifteen minutes of running and you will still see either black, white, or blue smoke, there is a definite engine issue behind it. So you will have to turn the mower engine off and wait for it to cool down.
Once cooled, check on the air filter. If it is congested, oxygen is not properly going through the combustion chamber. It results in an extremely rich fuel mixture that causes the engine to discharge smoke and function poorly.
The way to fix this is the substitute the air filter, which is a separate and easy chore.
Another situation might arise from spilling oil on the engine. It will emit either white or blue smoke. You might have mowed in steep incline, and the oil leaked out and poured over the engine.
It might look distressing, and yet it’s entirely harmless. You can fix the issue by restarting it and just letting the oil burn off from the engine.
If you usually angle the mower to its side for maintenance and cleaning, go through the mower’s user’s manual to find out the best way to do it without the dangers of leaking oil.
Black smoke
The most likely culprit for the engine smoking black is the air filter. The intermixing between air and fuel is too rich. Thus blackness is emitted.
Since air is lacking, combustion is not complete. The gasoline, which wasn’t properly burned, then turns to smoke.
The same thing happens when you burn dried leaves that are packed too tight to enable air circulation.
White smoke
The white smoke from the riding lawn mower has a few inceptions. It can look perturbing, but if it continues, most of the time, it will cease.
It usually comes from the engine burning oil, but it probably got there by accident. After maintenance, homeowners might have splattered some of it on the housing. Or the crankcase might be filled to the brim.
Possibly, the oil might have entered into the combustion chamber after turning the mower upside down due to blade cleaning. Even uphill mowing can enable the oil to leak over the combustion chamber.
If your mower has a two-stroke engine, you might have mixed in too much oil along with the gasoline. In normal conditions, it should only be between fifty to one and forty to one.
The extra oil won’t damage the engine. But if you regard too much smoke as an irritant, you need to replace the fuel.
A brand new mower will sometimes discharge white smoke when its engine starts for the first time. It’s because residual oil was left behind by the manufacturer.
You won’t need to call a professional technician for this, and you only have to let it run. The engine burns the residual oil, and the smoking will cease overflowing.
Blue of white smoke might be an issue
An excessive outpouring of either white or blue smoke could signify that the oil has created a passageway towards the combustion chamber through fagged seals. If it’s due to that, then there is a big problem in your hands.
The mower will continue its smoking ways, and the engine might cease to function. The reason for this might be a breach in the breathing tube, whose chief purpose is to direct air to the exhaust port from the combustion chamber.
Another cause might be a head gasket that’s blown to bits, resulting in oil soaking the air filter. This fix can only be done by a professional repairman. So you have to contact one.
Other probable causes for smoking mowers
If the smoking issues continue, the culprit might be the engine lubricating system, within the components where there are oil seals. Or maybe a crankcase snapped in half or something wrong with the pistons.
Another reason might be from the carburetor itself, it might need cleaning or adjusting.
These issues are easily fixed by a professional repairman. For carburetor adjustment, the user’s manual will provide instructions concerning this.
Still other possible causes
- Malfunctioning crankcase breather
- Filling too much oil in the crankcase
- Wrong oil grades
- Engine is functioning at an angle greater than fifteen degrees
- Busted head gasket
- Worn out cylinder and its rings
- Turning the mower upside down or on its side for maintenance purposes or storage
- Oil capacity in the engine has exceeded as seen on the dipstick
- Piston or cylinder rings are damaged
- Something blocking the breather tube situated behind the filter
What does it mean when your lawn mower smokes?
What causes a lawn mower to smoke?
A typical gas-powered lawnmower has either a two or four-stroke engine. Its mighty power comes mini-explosions inside the combustion chamber.
Similar to all reactions to combustion, it needs oxygen to achieve that. If the air isn’t enough and combustion isn’t complete, the fuel that didn’t burn becomes carbon deposits looking like soot.
These deposits amass in the spark plug’s terminal that extends to the combustion chamber or expels out of the exhaust as black smoke.
An engine that that emits a lot of smoke does not operate in full blast. If this will go on unfixed, the carbon will build up and deposits on the spark plug. Eventually, it will halt ignition.
Troubleshooting
If you want to know how to stop a lawnmower from smoking, follow these few simple instructions. Most of these are maintenance procedures, which you will regularly need to do for your gas-powered mower:
Clean the spark plug
Why is my lawnmower smoking, you may ask? It originated from the spark plug. You will have to clean or replace it.
First, pull out the boot and use a socket wrench to loosen out the plug. Observe closely its terminal.
If you can find thick carbon deposits, use a file or sandpaper to get rid of them.
If you either have a push or riding mower that has a four-stroke engine, and there are oily deposits plastered throughout, you might have a fagged oil seal.
You can get the mower engine running again by cleaning or substituting the spark plug. Yet smoking will persist till you fix the seal.
Reestablishing airflow
Another cause for not enough air going to the combustion chamber is an unclean air filter. You should make it a habit to regularly clean it, but people tend to easily forget it.
So whenever the filter gets grimy, it prevents the air from entering. The filter is not difficult to take out and clean, but the process to do that will be dependent on the make of your mower.
Most air filters are situated on the mower engine’s side portion and enclosed in a plastic case that’s stuck in place by a screw. Some you can throw away and replace easily, some you have to wash with soap and water.
There are mowers with paper filters that you can clean by blowing the grime out with pressurized air. Some have filters made of foam that are washable and used again.
The mower’s muffler can become congested and halt airflow coming from the combustion chamber. You can take it apart and use a wire brush to clean the sooty material off, or you can replace it.
To stop burns from occurring, let the muffler and mower cool down first before taking them apart.
Carburetor adjustment
Carburetors in small engines like lawnmowers have two or three adjustment screws. One screw to adjust the idle speed, the other one or two are for air-to-fuel adjustment.
Whenever the small mower engine emits black smoke, it can originate from the low-speed screw with an L marking. It might have been opened too far.
To fix it, look for the adjustment screw in your mower, which most likely is situated underneath the air filter, and turn the low-speed screw one-fourth to one-half clockwise using a screwdriver. It, in turn, creates a leaner mixture of fuel.
Whenever you’ll make this sort of adjustment in the future, you will find out your mower engine will have a better sound. It’s due to the fuel is burning efficiently.
Drain excess oil
Small lawn mower engines need about one-half quart of oil. So homeowners usually make the mistake of overfilling it. Many will pour it in without even checking on the level. They might think this is harmless and doesn’t cause distress to the machine.
Too much oil will cause damage since most mower engines have a splash lubrication system. Whenever oil goes above the splash paddles, they will not function effectively.
You have to drain the extra oil and let the mower remain idle until the smoke disappears. It will take a couple of minutes of your precious time.
Remove oil from gas tank
It is a common occurrence to accidentally pouring oil into the gas tank. To fix this, you will have to drain the tank of all the gasoline to clear out the engine system and let it run its course.
Once you’ve added back the fuel and the engine won’t start, you have to either adjust or clean the carburetor.
Remove oil from carburetor
Whenever there is white smoke, it may be because oil has gotten into the carburetor and obstructing the gas feed jet.
You can start the engine a few times to clear it out or keep the engine running until it dissipates. But if the engine sputters and does not run for longer periods, you will have to clean the carburetor.
Try to tilt the engine to discharge the oil from the cylinder or remove the spark plug and clean it. If the issue still prevails, take out the carburetor and clean it.
Still other troubleshooting tips
- Whenever tilting the engine, make sure the spark plug is facing directly up to prohibit oil from coming out of the crankcase.
- Regularly check the oil and change it if it needs changing. Examine if it’s overflowing to the brim or using an incorrect type or grade.
- Whenever you need to tilt your mower for any purpose, be sure it’s less than a fifteen-degree angle. Tilting it can result in leaks. Make sure this is amended before you mow for the day.
- Check the crankcase regularly for any leakage.
- Regularly check if the gasket is fine and not busted.
- Check if the cylinder and its rings are worn out.
- If you detect oil in the engine, let the mower run its course till the oil is burned off.
Conclusion
After attempting all the troubleshooting methods and still, your mower is smoking, your next option would be to call a professional mower technician. Don’t try to fix it on your own, or else it might get worse.
