Can You Run A Lawn Mower Without A Muffler? (5 Reasons It is a BIG Risk). Riding lawn mower muffler

Can You Run A Lawn Mower Without A Muffler? (5 Reasons It is a BIG Risk)

Much like any piece of machinery a lawn mower is a series of complex parts that all work together to help you keep your lawn in check.

We know that some parts are crucial and without them your mower won’t function, but there are some that it seems it might be able to do without.

Can you run a lawn mower without a muffler for instance?

Surely it isn’t that important?

Can You Run A Lawn Mower Without A Muffler?

You can run a lawn mower without a muffler, but you shouldn’t for a number of reasons. It will mean your mower is much noisier for both you and your neighbors, it will make it more of a fire risk and it will mean there is much more likelihood of you damaging the engine and valves.

Running a Lawn Mower Without a Muffler: The Bottom Line

You most certainly can run a lawn mower without a muffler.

In fact, reel and battery mowers don’t have mufflers, but that is because they don’t burn fuel.

But you can even run a gas mower or a riding mower without a muffler.

But the big question isn’t can you run a lawn mower without a muffler? But instead, it is should you run a lawn mower without a muffler?

That answer is ‘No’, it simply isn’t worth the risk.

So what is the risk you ask?

We will delve into that now.

#1: It Will Be Very Noisy

Running a mower without a muffler opens your mower up to a multitude of problems.

The engine was designed to run with a muffler on and without it there will be a loss of back pressure.

Back pressure is the pressure that is held or maintained to allow the engine to produce a predetermined amount of horsepower and torque.

So without a muffler you will lose power and the mower will not run as well.

#5: It Will Damage the Valves and Other Engine Parts

The muffler is right next to the very hot exhaust valves. When the engine is shut off, it holds this heat and allows the valves to cool slowly.

However, if you don’t have a muffler when you shut the engine off, cooler air will be able to rush into the exhaust valve and cause it to bend from cooling too quickly.

If that happens the engine will lose compression and you will have to pay to have the valve replaced.

Many racing cars don’t have mufflers, and you will often notice the exhaust pipes being covered or plugged to keep cool air out for the very reason mentioned above.

Additionally, without a muffler to absorb heat, it means other parts of the engine, such as the carburetor, are more likely to come into contact with hot exhaust gases and be damaged.

Final Thoughts

A muffler works by smoothing the pulses from a lawn mower engine into a continuous flow of gases.

However its primary job isn’t to reduce noise, but actually to prevent exhaust sparks from existing and igniting dry grass, leaves or any other debris around.

If you use your lawn mower without a muffler it will be much louder and could damage your hearing, even with ear plugs in, and annoy your neighbours.

It will also be a safety risk. The chance of a spark escaping and setting dry grass on fire is small, but it will be present if your lawn mower doesn’t have a muffler.

On top of all of that running a lawn mower engine without a muffler means there is an increased chance of you damaging the valves or pistons or blowing a head gasket.

If you do it once out of necessity, you might get away with it. But it certainly isn’t something you should consider doing long term.

Introduction: Homemade Exhaust for Your Old Lawnmower

You can build your own, homemade exhaust system for an old Briggs and Stratton lawnmower engine!

When taking my junk-picked 70s-era lawnmower apart, besides finding out that this motor was made the same year I was, I realized that the exhaust threads are a standard pitch 1/2 inch pipe thread!

The parts you will need are: A short 1/2 inch nipple (short pipe, threaded on both ends) A 1/2 inch x 1 inch hex bushing (female 1/2 inch on one end, male 1 inch on the other) A 1 inch 90 degree elbow A length of 1 inch pipe A 1 inch cap A drill and small drill bit(s) Cutting oil for drilling (WD-40 or even motor oil will probably work) (optional) Pieces of fiberglass tape or cloth for sound-deadening material.

PLEASE use black gas piping, NOT galvanized pipe. Galvanized pipe is coated inside and out in zinc. Zinc heated to very high temperatures can offgas and make you feel very sick. There is some debate as to whether zinc exposure leads to long term health effects, but I have gotten some stern warnings against welding zinc, so have used only black gas piping for this project.

You could also probably do this project with aluminum or threaded copper pipe, but for safety and affordability, I went with the steel. You probably wouldn’t want to use soldered copper, in case the solder were to melt and cause trouble.

Step 1: Remove Old Muffler

On these old engines, the muffler is easy enough to remove. Simply unscrew it from the engine block. (lefty loosey, and please do this when the muffler is cold!)

Step 2: Assemble the Manifold

The manifold (Part of the muffler that attaches to the engine block) is easy to make from a threaded nipple, a hex bushing and a 90 degree elbow.

Assemble these parts tightly. Depending on the final required orientation of the muffler, it may be necessary to attach some parts with a bit of fiberglass tape to allow more flexible positioning of the joints. Here, I used fiberglass cloth left over from a canoe pontoon project, but you could also use fiberglass drywall tape. You might not require the fiberglass at all. I didn’t use plumbers tape because I was concerned about the heat generated by the muffler burning the tape and causing a stink.

Step 3: Fabricate and Assemble the Muffler Body

To make the muffler body, I used a 12 inch length of 1 inch diameter pipe, into which I drilled 5 3/16 inch holes. I discovered that two holes was not enough and 5 seemed to be OK. You can experiment with the number of holes if you like, and a 12 inch pipe is probably overkill.

Before and during drilling, I wet the steel with WD-40 (cutting oil may work better) to cool the drill bit so as not to wear it out. The metal is quite thick and I broke 2 drill bits by trying to rush things. Take your time and use plenty of oil.

After the holes are drilled, clean up the pipe to remove any metal particles and cut a short length of fiberglass tape. Roll it up and stuff it into the end of the tube. The fiberglass will serve to deaden the noise a little,but it may also come flying out of the exhaust holes when the engine is running. It helps to cut the fabric as little as possible so as not to create many loose threads.

Screw the pipe cap on tightly. You can remove the cap or disassemble the muffler entirely to repack or repair it in the future.

Step 4: Attach the Muffler

The original muffler has a stop on it to prevent you from over-tightening it and stripping the threads. Your new muffler will not have this safety feature, so be careful when threading the new unit into place. The engine block is aluminum and very soft in comparison to the steel pipe. Do not use a wrench to thread the pipe into the block. hand tight is plenty.

Once you are satisfied with the tightness and orientation of the manifold, screw the muffler body into it. You have a muffler!

You should now be ready to test the exhaust. Be careful when testing and running the engine!

1) The new muffler is much heavier than the old muffler, and may cause stress damage to the engine block if it is not installed and supported properly. 2) The fiberglass tape may come out of the exhaust holes. be aware of this and on alert in case the engine decides to suck up a strand. 3) The muffler gets VERY hot, VERY fast. Do not EVER touch a muffler after running the engine for more than a few seconds. 4) Please do NOT use galvanized pipe. Only use black gas piping. Galvanized pipe is coated in zinc and when exposed to extreme heat, it could offgas and make you feel very sick. My original attempt was with galvanized pipe, and I got a bit light headed after the muffler heated up for the first time. Also never weld galvanized metal for the same reason.

Please be careful. This project involves extreme temperatures, hot gasses and fast moving parts. Do not rush things and be always aware of where your hands and feet are in relation to the mechanisms.

Step 5: Fit and Finish

The final steps are up to you. The muffler may need extra support, which could be accomplished with cleverly placed bolts, hose clamps or pipe support straps. Use your head and think of where the forces are going to be transferred.

Dress up your exhaust tube and add a margin of safety with an exhaust tip or cover.

Don’t be afraid to experiment with the amount of packing material, number, size and placement of holes, etc. This muffler is completely customizable.

I originally designed a much smaller muffler with larger diameter pipe, but when I moved to the black gas pipe, the larger pipe diameters were not available.

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Комментарии и мнения владельцев

Do you think this would work for a 12 HP Briggs engine in a Ride-on mower? Would it need extra holes do you think?

haha, nice. I used to do alot of mower modifications before I got a car, now I modify my car. I have an old lawn mower engine that I think puts like 15-20 horsepower with the things I’ve done to it. I want to rebuild it and make around 50 horsepower by turbocharging it. but that’ll be sometime later

imposiblle i fix these for a living and the fastest you can posiblie make the one above go before it blows is about 9-10 and a half HP

DISCLAIMER: UNDER NO CIRCUMSTANCES DO I ENCOURAGE ANYONE TO DO OR TRY ANY OF THE THINGS I MENTION BELOW EVER ANYPLACE!! I am sharing this information only to illustrate the extremes bored farm kids will take to amuse themselves!

RE: Horsepower, Depends on “what else” you do to the motor. On a horizontal 3HP Briggs (old water pump motor turned minibike engine) we planed the head(ourselves), replaced the head gasket with high temp silicone. Ported the intake and exhaust (we called it a Y head instead of L Head), ground the sides off the cam lobes and welded a bead on the top (using nickel rod) to increase lift and decrease duration. Advanced the timing (pretty far) by moving the crankshaft detent for the points ahead. We also ran Dads “racing gas” (125 octane sprint car fuel”. Also tried 60/40 Gasohol in the same setup, and Methanol (with a Harley Davidson Carburetor). With the Harley carb, it would carry 3 boys and spin the rear tire using the cheesy centripetal clutch. All this without the governor of course. We were told we were likely getting 10-15 HP out of it. (WE WERE VERY VERY LUCKY the flywheel didn’t explode. but like Wile E. Coyote, we didn’t know how many RPMs it was turning, so we survived. If ANYONE is going to go that extreme with a motor, you definitely need a billet flywheel and metal shields around the flywheel (not tin), and steel angle irons or metal bars above the head and below the block all-thread rod-ed together) to hold the engine together.

that doesn’t make any sense since 5hp blocks are used in mini-dragsters for kids to make over 50 HP. Mine has a modified cam, custom piston, custom rod, custom crank, custom intake manifold, exhaust that’s so little that it’s not even telling the truth if I said it had exhaust, and modified intake and exhaust valve ports

Maybe you could have used stainless steel scrubbing pads to prevent the engine from sucking fibers in. Thanks for the idea, I have a lawnmower with a similar engine and was looking for a way to silence it. You rock!

My thoughts as well. if you put that in “loose” it might baffle it pretty well, though I think that would be outside the pipe with the holes in it.

I dont think thts a 70’s Lawnmower its horizontally shafted most in the 70’s were verticle with rollers AND from my view it looks like a 4hp Briggs and stratton engine But if it is i stand corrected

It could well be a 70’s or 80’s mower. Not as many self propelled mowers like today, and really no honds to speak of. Simplicity, the “cadillac” of mowers had a self opropelled mower that used a knurled roller on larger back wheels to drive it. MTD was not a huge player, and there were still lots of Montgomery ward, Sears, Coast to Coast, True value, and mom and pop stores that sold pretty generic mowers like this.

Are you sure? from the looks of it that is a pushmower which almost always have vertical shafts. Especially on this one where the shaft goes down to spin the blades and the sticker on his mower (last picture on the last step) says 3.0HP

yes vertical shaft ioalways get the two mixed up but i can tell you a 3hp briggs and stratton wouldnt be fitted to a 70’s lawnmower youd have a suffolk iron foundry engine or a Villiers. I restore them and take them to classical shows etc

OK, I see some problems here. 1. This idea needs to have the amount of backpressure figured out so you don’t burn the valves or cause power loss. 2. I have seen pipe systems like this before and the weight of the pipe usually wears out the threads in the engine because you cannot keep them tight. 3. Spark arresting features of this system probably will not meet US Dept. of Forestry specs. 4. Might be more dangerous if fuel is spilled on the mower. 5. Bigger exhaust system = more possibility of skin burns or setting dried grass on fire. 6. The cost of the pipe and fittings is way more than the 2-3 for an approved muffler.

On the plus side, it looks cool, especially with the chrome cover.! LOL!

First things first. You’re a killjoy, and if you’re so worried about obscure, irrelevant and stupid regulations and rules, then what are you doing on this website? I’m really quite serious. I know I read three articles on bomb-making and two about lockpicking before breakfast. 1. The brilliant thing with projects like this is the overkill. Drill more than enough holes and it won’t cause any back pressure. 2. So far as the stripping or cross-threading is concerned, the man even suggests supporting the weight somehow. Also, it’s a thirty-year-old law mower, what does it matter if it does strip? He can take the entire muffler off and have a SUPER loud lawnmower just for the heck of it. 3. Who cares? 4. Oh, wow. My lawnmower is on fire. Hold on while I call a few people to come over and watch and maybe bring some thermite so we can do this right. 5. Oops. I burned myself on an exhaust. Again. I’m tattooed up both arms and legs from exhausts from motorcycles and cars and ovens and god-knows what else. Go somewhere else if you’re going to live in fear of life. Some of us do things with the full expectation of getting hurt. It’s half the fun to have a scar to associate with something really fun or really stupid your did. Most times both. 6. Did he ever mention this was going to be a money-saving endeavor? The whole point of this is that the stock muffler wasn’t quiet enough for this man’s liking, so he built a bigger one and put a chrome tip on it. Just because he could. Welcome to America, a country founded upon the principal of experimentation, the Rule of Cool, and getting away from killjoys. I, for one, would try to make an exhaust cover like they put on the AC Cobra’s side pipes, or maybe built a mini diesel smoke stack just to make it look cooler. I bet with a little welding and some pre-planning, you could give your lawnmower twice-pipes. I’d absolutely love to try this on a gas-powered rotary mower, just for the look. Maybe even vent the exhaust to the side, and put a spark plug in it hooked to a battery. Nothing says “Good mornin’!” like flaming exhaust when you’re mowing the lawn. Maybe you could even vent it straight up and brace it, so everyone can enjoy the flames.

I so so so SO SO SO so so SO SO SOOOOOOO agree 100% with what you said here. Thank you! Ideas like this is why I LOVE this site so much!

You know something, I really don’t care what anybody builds here. All I tried to do is make sure the builder is being careful to make sure he isn’t hurt, maimed, or killed. If any of the three happened to the builder, I’m sure it would kill somebody’s joy in a hurry. Let’s not call people names and criticize why they are here. Every year someone modifies a lawnmower in a way that causes them pain or death. The next thing that happens is that the manufacturer and the dealer get sued. I don’t care what anybody builds here but please be careful and when things go wrong, take responsibility for any negligence on your part.

Firstly, nobody called you a name. Calling you a killjoy is no more calling names than saying that someone who runs professionally or competitively is a runner.

Secondly, you are again being incredibly offensive by, effectively, calling the builder a moron incapable of foresight or any knowledge of safety. For all you know, this gentleman is an engineer who designs two-stroke engines for NASA, or some other type of engineering Hyper-genius. Both of your posts are insulting and degrading to the gentleman who wrote this article and I am, again, deeply offended by your treatment of someone who took time out of his life to share his experience and ingenuity and bring a smile to people’s faces. So, because of your condescending posts, I’ll respond in kind.

“You know something, I really don’t care what anybody builds here.””I don’t care what anybody builds here. “- Then why did you bother to comment in the first place?

“All I tried to do is make sure the builder is being careful to make sure he isn’t hurt, maimed, or killed.”- Via a text post, after the fact, online, anonymously, with alleged “facts” of things that are so improbable it’s insulting? Also, this contradicts your previous statement that you “care what anybody builds here”. Has the Nobel committee been made aware of you?

“but please be careful and when things go wrong, take responsibility for any negligence on your part.”- LOL. What?

“Spark arresting features of this system probably will not meet US Dept. of Forestry specs.”- Please submit a detailed diagram of exact blue-prints of the builder’s design and highlight the specific faults you have found. Also, please post the specific and applicable “US Dept. of Forestry specs” along with exactly how they affect this build. Please cite your sources.

“Every year someone modifies a lawnmower in a way that causes them pain or death.”- Please list specific examples of both death and injury each year starting from the invention of the lawn mower by Edwin Beard Budding in 1827. Please cite your sources.

“I have seen pipe systems like this before and the weight of the pipe usually wears out the threads in the engine because you cannot keep them tight.”- Please cite each and every specific instance you have personally had direct experience with. Please note dates, locations, and potential witnesses. Also, please post the exact weight of the exhaust system the builder implemented, along with equations to prove your hypothesis. Please show the exact torque at the fulcrum and detail the exact tolerances of the materials and threads on both the engine block and the exhaust system. Please cite your sources.

“5. Bigger exhaust system = more possibility of skin burns or setting dried grass on fire.”- Please explain how. The chrome tip on the exhaust will actually act as a heat shield as there is minimal contact with the muffler, and the exhaust is not venting openly, but inside the tube of the exhaust tip which would act as a crude flame arrestor along with the fibreglass inside. Plus, the muffler is pointing forward, away from the operator position, which would severely diminish the likelihood of ever coming in direct physical contact with it. Also, note the builder’s own writing, “Dress up your exhaust tube and add a margin of safety with an exhaust tip or cover”.

“6. The cost of the pipe and fittings is way more than the 2-3 for an approved muffler.”- Please cite examples. Lawnmower mufflers can cost up-wards of 11 or more (http://www.amazon.com/b?ie=UTF8node=155375011). Please list for us the exact model number of the specific “approved muffler” for this engine, along with a website showing an average price a consumer could expect to pay in USD. Please cite your sources.

“1. This idea needs to have the amount of back-pressure figured out so you don’t burn the valves or cause power loss.”- How do you know the builder did not? He, in fact, states quite clearly that, “I drilled 5 3/16 inch holes. I discovered that two holes was not enough and 5 seemed to be OK”. Please list the exact exhaust pressure for this specific model of engine, taking into account it’s exact current age and operating condition. Please also note what the optimal operating exhaust pressure range should be, taking into account weather and other operating conditions, and an equation showing exactly how to calibrate a custom muffler to operate within these specs. Please also note the exact amount of back-pressure created by the current exhaust system and note whether or not it is operating within acceptable tolerances and, if it is not, how to modify it to bring within the optimal operating specs. Please cite your sources.

Please also list any degrees, certifications, qualifications, and/or training you have that make you qualified to provide criticism on this project, including your practical experience with federal regulations. Please cite your sources, examples, and proof of above.

In the future, you may want to try acting like less of a buzz-kill and just enjoy things. You don’t need to be condescending, rude, confrontational, or even just plain mean to get attention or start a conversation. Perhaps a better way of approaching the matter would have been to ask, “Hey, have you had any problems with the back-pressure or it flaring up on you”. That would have brought his attention to your concerns, over what you perceive to be a death-trap, in a neutral, non-confrontational, and almost friendly way. Then it leaves the door open for him to say if he has had the problems and, if so, how he resolved them, or to note that he hasn’t and won’t have the problems because he took things into account.

Something to keep in mind is that most of us who tinker around with these, and more potentially dangerous projects, are most usually pretty darn aware of not only the physics and chemistry of what we’re playing with, but the safety precautions as well. This project is about as far from dangerous as one can get without using Play-Do, yarn and blunt-tipped scissors. The engine is so under-powered that even if he had completely plugged the exhaust, nothing more dangerous would likely have happened except the engine dying.

You could have handled this all much better and in a far nicer way. You could have at least approached this in a manner that didn’t involve insulting people and coming off as such a condescending, arrogant, and mean person. I’m not saying that you are any of these things, just that you are coming off as such. You could have just been social and human.

Perhaps this can all end here, as I know that I won’t bother responding to any further posts here. This is the end of my fun and it’s going to just get dumb after this. I really can’t believe that you are so oblivious about your behaviour, but perhaps you will keep it all in mind next time you post a comment to a project someone posts and is obviously proud of. Tearing people down is not the way to get positive attention. In the end, however, there’s certainly nothing more for you to say as I’ve really kind of put you in a corner. So let it drop and walk away or you’re going to look silly. This isn’t a fight, so just be human and social.

Good luck in your future endeavours. I really do mean that.

How to Make Lawn Mower Quieter?

David Ogbonyomi. 11 Jun 2020

I love mowing my lawn because nothing beats a home that has a beautiful and well-trimmed lawn. However, I was always reluctant to mow my lawn whenever I remember the noise produced by my lawn mower and also the complaints I received from my neighbors about my mower disturbing the entire environment. I had to find solutions and ways to make my lawn mower quieter.

Most lawnmowers are generally loud, and some produce noise as loud as 90dB, which is above the recommended level of noise for the ear. As much as it is possible to purchase a mower that produces less noise, not everybody can afford this luxury.

Our other guides you might also be interested in:

Here are some of the methods I use to achieve this:

Start with the Muffler

Most mowers have a muffler that is usually installed on the exhaust. This muffler helps in channeling sound that is produced by the engine through a noise-canceling chamber. A crack in the gasket seal between the muffler and the exhaust can lead to poor or no cancellation of the noise produced. It is, therefore, important to check the muffler when you notice your mower is noisy. This can be done by;

• Locating and removing the muffler from the exhaust to check for cracks and debris on the gasket.
• Peeling of the debris from the gasket or replacing the gasket if there are cracks on it.
• Pay attention to the dimension of the muffler you buy—shorter mufflers and generally noisier than longer mufflers.

Install an Engine Silencer

This is very helpful, especially with combustion engines. Engine silencers help in reducing the noise produced during combustion. There are two different types of engine silencer you can make use of; the reactive silencer, which is connected to the engine exhaust and helps in reducing low to mid-level noise, and the absorptive silencer which has fiberglass insulation that makes it a perfect option for reducing the noise of very high frequency. There is also an upgrade of these two, and that is known as the combination silencer. As the name implies, it is perfect for the noise of any level.

Check the Deck

Making use of soundproofing materials can help in producing a quiet deck and also in reducing the noise that comes from the rock pings, blades, and also from vibrations.

These are the methods I made use of and this is because of the complaints I received from my neighbors. There are other ways to achieve this, especially if you are trying to make the mower quieter for your reasons. You can make use of hearing protection gears when mowing. There are several ear muffs with great soundproofing qualities you can make use of. Another option is to buy a quieter mower. This is the best option, especially if you are unable to go through all the processes I’ve listed above. They are methods I used, and I’ve gotten the results I needed

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A smoking lawn mower is never a good sign. Whether the smoke is blue, white, or black, here’s how to identity and address the issue without the help of a professional.

By Glenda Taylor and Bob Vila | Updated Sep 24, 2020 1:40 PM

We may earn revenue from the products available on this page and participate in affiliate programs.

Q: Recently, my mower started billowing smoke when I powered it up, so I shut it off immediately. Why is my lawn mower smoking? And is it a fire hazard? I want to know how to proceed so I don’t harm the machine.

A: Your lawn mower can emit smoke for numerous reasons—many of which don’t require the services of an expert. A homeowner can usually identify the reason for a smoking lawn mower by gauging the color of the Cloud coming around the engine, then fix it accordingly before lasting damage occurs. Keep in mind that all mowers with internal combustion engines contain the same basic parts, but the configuration of those parts varies widely, depending on manufacturer and model. Consult your owner’s manual if you’re unsure how to access a specific part of your lawn mower’s engine.

White or blue smoke may indicate an oil spill on the engine.

If you’ve recently changed the oil in your mower and the engine is emitting white or blue smoke, it’s possible that some of the oil spilled onto the engine. Similarly, you could’ve spilled oil on the engine by mowing on a slope greater than 15 degrees or tipping the mower on its side. The smoke may look disconcerting, but it’s completely harmless. Solve the problem by restarting the mower and allowing the spilled oil to burn off. If you tip the mower often for cleaning or maintenance, check your owner’s manual to determine the best way to reduce the risk of oil leaks.

An overfull oil reservoir may also cause white or blue smoke.

Ensure you didn’t overfill the mower by checking the oil level with the dipstick located on the reservoir. To do this, remove the dipstick cap, wipe off the stick with a rag, and reinsert it into the reservoir. Then remove the dipstick once again and determine the oil level in comparison to the recommended “fill” line on the stick. If the level is too high, drain the oil (consult your owner’s manual for instructions), then refill the reservoir with it. Start checking the oil level with the dipstick after you’ve added about ¾ of the amount recommended in the manual. Continue to add small amounts of oil until the level matches the recommended “fill” line. Also note that using the wrong grade of engine oil may cause blue or white smoke. Consult the owner’s manual for the exact type of oil recommended for your mower.

Black smoke may indicate that the mower is “running rich,” or burning too much gasoline.

Your lawn mower’s carburetor regulates the ratio of gasoline to air mixture. If the carburetor isn’t getting enough air, the mixture has a higher percentage of gasoline, which can create black exhaust smoke. It’s possible that a dirty or clogged air filter is preventing sufficient airflow into the carburetor. Try replacing the air filter. (Note: air filters vary by mower model; view example air filter on Amazon.) Next, run your lawn mower for a few minutes. If the black smoke still appears, the carburetor might need to be adjusted in order to increase airflow. Either take the mower to a professional or adjust the carburetor yourself with instructions in your owner’s manual.

Take your mower to a repair shop if necessary.

If the previous steps don’t correct blue or white smoke, your mower could have a more serious problem, such as an air leak in the crankshaft (the cast iron or cast aluminum case that protects the moving parts of a mower’s engine). Continuing blue or white smoke could also indicate that some of the engine’s components or seals are worn out and need replacement. Similarly, if black smoking still persists after you’ve replaced the air filter and adjusted the carburetor, you could be facing a more serious mechanical issue. All of these problems require the help of a professional. If your mower is still under warranty, check with the manufacturer for the location of the nearest servicing dealer; problems stemming from a factory defect or poor workmanship may garner free repairs. If your mower is not covered under warranty, a reputable small-engine repair shop should also be sufficient to get the job done.

A smoking lawn mower is never a good sign. Whether the smoke is blue, white, or black, here’s how to identity and address the issue without the help of a professional.

By Glenda Taylor and Bob Vila | Updated Sep 24, 2020 1:40 PM

We may earn revenue from the products available on this page and participate in affiliate programs.

Q: Recently, my mower started billowing smoke when I powered it up, so I shut it off immediately. Why is my lawn mower smoking? And is it a fire hazard? I want to know how to proceed so I don’t harm the machine.

A: Your lawn mower can emit smoke for numerous reasons—many of which don’t require the services of an expert. A homeowner can usually identify the reason for a smoking lawn mower by gauging the color of the Cloud coming around the engine, then fix it accordingly before lasting damage occurs. Keep in mind that all mowers with internal combustion engines contain the same basic parts, but the configuration of those parts varies widely, depending on manufacturer and model. Consult your owner’s manual if you’re unsure how to access a specific part of your lawn mower’s engine.

White or blue smoke may indicate an oil spill on the engine.

If you’ve recently changed the oil in your mower and the engine is emitting white or blue smoke, it’s possible that some of the oil spilled onto the engine. Similarly, you could’ve spilled oil on the engine by mowing on a slope greater than 15 degrees or tipping the mower on its side. The smoke may look disconcerting, but it’s completely harmless. Solve the problem by restarting the mower and allowing the spilled oil to burn off. If you tip the mower often for cleaning or maintenance, check your owner’s manual to determine the best way to reduce the risk of oil leaks.

An overfull oil reservoir may also cause white or blue smoke.

Ensure you didn’t overfill the mower by checking the oil level with the dipstick located on the reservoir. To do this, remove the dipstick cap, wipe off the stick with a rag, and reinsert it into the reservoir. Then remove the dipstick once again and determine the oil level in comparison to the recommended “fill” line on the stick. If the level is too high, drain the oil (consult your owner’s manual for instructions), then refill the reservoir with it. Start checking the oil level with the dipstick after you’ve added about ¾ of the amount recommended in the manual. Continue to add small amounts of oil until the level matches the recommended “fill” line. Also note that using the wrong grade of engine oil may cause blue or white smoke. Consult the owner’s manual for the exact type of oil recommended for your mower.

Black smoke may indicate that the mower is “running rich,” or burning too much gasoline.

Your lawn mower’s carburetor regulates the ratio of gasoline to air mixture. If the carburetor isn’t getting enough air, the mixture has a higher percentage of gasoline, which can create black exhaust smoke. It’s possible that a dirty or clogged air filter is preventing sufficient airflow into the carburetor. Try replacing the air filter. (Note: air filters vary by mower model; view example air filter on Amazon.) Next, run your lawn mower for a few minutes. If the black smoke still appears, the carburetor might need to be adjusted in order to increase airflow. Either take the mower to a professional or adjust the carburetor yourself with instructions in your owner’s manual.

Take your mower to a repair shop if necessary.

If the previous steps don’t correct blue or white smoke, your mower could have a more serious problem, such as an air leak in the crankshaft (the cast iron or cast aluminum case that protects the moving parts of a mower’s engine). Continuing blue or white smoke could also indicate that some of the engine’s components or seals are worn out and need replacement. Similarly, if black smoking still persists after you’ve replaced the air filter and adjusted the carburetor, you could be facing a more serious mechanical issue. All of these problems require the help of a professional. If your mower is still under warranty, check with the manufacturer for the location of the nearest servicing dealer; problems stemming from a factory defect or poor workmanship may garner free repairs. If your mower is not covered under warranty, a reputable small-engine repair shop should also be sufficient to get the job done.