atv exhaust pipe releases white black and blue smoke

Why Does My ATV Smoke? [White, Black, or Blue Smoke?]

Last weekend I had started up my ATV and noticed some smoke coming out of the exhaust for what seemed to be an incredibly long time.  It had me panicked because the last time I used it, I had heard a very slight “knocking” noise that I couldn’t quite pinpoint. After nearly one minute, the smoke completely dissipated and I was off to the trails.  I did some research on what your smoke can be telling you about your four wheeler and here is what I gathered.

Why Does Your ATV Smoke?

Your ATV can smoke for one of 3 reasons: 1) black smoke is generally benign and is due to an overly rich fuel mixture 2) blue smoke is a bigger concern and is due to cross contamination in the air fuel mixture within the cylinders 3) white smoke is typically water droplets being burned off as steam, but can be a very bad sign if it doesn’t go away within 60 seconds.

Let’s look into each of these more in depth.

Black Smoke

What is black smoke and why does your ATV release it?

If you notice black smoke being released from your exhaust there is generally NOT a larger underlying issue to worry about and it is a relatively benign occurrence due to an overly rich fuel mixture and not enough air intake.  That being said, there ARE some causes of black smoke that are more costly to repair than others, below are a few general reasons why this occurs:

  1. Not enough intake of air into the cylinder
  2. Abundance/excess of fuel (similar to the 1st reason but exactly the opposite)
  3. Faulty fuel injector/carburetor
  4. Improper selection of fuel
  5. Engine block overheating
  6. Faulty controller (similar to the 3rd reason but the controller itself is faulty vs the injector)
How to troubleshoot and fix black smoke

I know it probably makes you nervous to see that your 4 wheeler is smoking and I don’t blame you, but you’ll find that the troubleshooting and repair process on black smoke is relatively simple, let’s take a look:

Check #1

Inspect your air filter for cleanliness (or lack thereof).  This is by far the number one reason why your quad isn’t intaking enough air into the cylinder.  Many riders go far too long without ever inspecting it and then wonder why they have lost so much power and why the exhaust is releasing unwanted black smoke.

This is a very simple and cheap fix and should be done frequently, especially if you are riding through rivers or streams and more importantly heavy mud since your air filter will absorb and collect it.  Mud is a great way to clog up an air filter but so is the dust, dirt and other gunk you tend to ride through.

Bugs, grass, twigs and other residues collect in your air filter so check it often (ideally before every ride) to make sure enough air is entering the cylinder and to allow for the proper fuel mixture.

How to Clean Your Air Filter:

Cleaning a paper air filter is easy, just take the air filter out of the chamber and beat it lightly against your palms.  You should see most of the dust and dirt flying into the air and you should notice the filter turning a whiter color.

Keep beating it against your palm until it looks as though much of the larger debris has fallen to the ground and out of the filter.  If it looks torn or overly worn, it’s probably time to invest in a new one.

Foam filters are slightly more involved, but still a simple process.  Get two small buckets and fill the one with a filter cleaning solution to get most of the gunk out being careful not to twist, pull or rip the foam filter.  

When you’ve cleaned out the heavier stuff from the filter then take the other bucket with the similar air filter cleaner and gently massage out the finer particles that are left in the filter.  When done, let the filter air dry for a couple of hours. After air drying, you’ll want to lightly lubricate the filter and airbox of the machine and give it another couple of hours.

Check #2

Do a quick temperature check to see if the other cylinder (if your four wheeler has multiple cylinders) has a lower temperature.  You can do this by touching the exhaust manifold after starting up your quad. If the other cylinder isn’t as hot as the other then it’s an indicator that you may have a clogged or seized fuel injector that needs to be replaced.

Check #3

Listen carefully to your engine for any abnormal noise coming from the cylinder head(s).  You could be hearing a noise due to an improper valve clearance that needs to be adjusted.  All ATV’s have a standard clearance that sometimes becomes lengthened or shortened after heavy use of your quad.  

Using a feeler gauge to check for the proper clearance can tell you right away if that’s the cause of the knocking and the black smoke.  If so, your local mechanic can adjust it for you or you can do it yourself with the right tools.

Blue Smoke

What is blue smoke and why does your ATV release it?

Unlike black smoke that is an unbalanced mixture of air and fuel, blue smoke indicates that your engine is burning oil through the cylinders and that the oil is escaping out of your exhaust.  If you’re seeing blue smoke coming from your exhaust, you want to pay particular attention to your oil levels. The more often you have to refill, the bigger the problem is.

But why does this problem even occur?  Each engine has valves that open and close and are governed by rocker arms.  As the valves go up and down the allow air and gasoline to enter the cylinder where they combust and distribute the power to the wheels.  

The problem exists when the contact between the rocker arm and the valves also allow oil to enter the combustion chamber where it interacts with the air/fuel mixture releasing blue smoke from the exhaust.

Most commonly the oil seeps through because the valve seals are worn, cracked or broken.  Here are a couple of ways to remedy blue smoke coming out of the exhaust…

How to fix blue smoke

Get an Engine Cleaning

This is where I would start if you have a poor maintenance record for your quad.  As i said above, riding through dirt, mud, sludge and other sloppy conditions can really take a toll of your 4 wheeler, especially when you let it harden without washing down your quad.

To do this you can simply remove the valve cover and clean the surrounding area that could be full of oil and debris.  This may not do much, but it’s a really good habit to get into to increase the lifespan of your machine. When you’re done cleaning just put the valve cover back on tightly.

Fix the Valve Seals

Fixing the valve seal is more involved than getting an engine cleaned (and beyond the scope of this particular blog post) but if you just don’t have the time to invest in doing it yourself then any mechanic should be able to properly replace the valve seals for you.  

Properly replacing valve seals should only take a reputable mechanic about 2-3 hours of work and translate into about $200-$300 in repair costs.

But if you decide to take on the challenge yourself, the big takeaway is not to drop the valve into the engine, you’ll want to keep the valve pointed up, and to do that, most people use compressed air that gets directed upward via the spark plug opening.

If you don’t have the tools, or the time, i’d recommend having a professional do it, it’s relatively cheap and they will guarantee their work.

White Smoke

What is white smoke and why does your ATV release it?

White smoke coming from the exhaust of your ATV can be an extremely benign issue or it could be a large issue which needs addressing right away.  The simple way to check it’s severity is simple, here is how you can tell.

If your ATV lets out a cloud of smoke immediately upon starting, but then dissipates completely after a few seconds then it is likely just a matter of water droplets being evaporated and escaping through the exhaust pipes.

You’ll usually notice this on cooler mornings especially if you used your 4 wheeler the day before.  It isn’t of much concern unless you notice it getting worse and worse.

Now if you notice a cloud of smoke immediately when the engine starts but then continues minutes after the engine has started (or during a healthy acceleration) then something more severe is going on inside the engine block.

Heavy white smoke is a sign of an internal coolant leak and the smoke is also accompanied with a sweet odor and a low coolant level.  Check your coolant level to see if you are low (never with the engine running or hot), if so, try accelerating while in park/neutral mode.

Does the exhaust release a thick, milky, frothy white cloud of smoke?  If so, the chances are high that you have a warped or cracked cylinder head, engine block or some variation of a head gasket failure.

But how did it get like that?

Dirty coolant, a poorly maintained cooling system, excessively low levels of coolant or a cooling fan that doesn’t work well can all cause one major engine problem – overheating.

Also, normal engine wear can cause head gaskets to lose their capacity to seal properly, allowing some coolant loss.  Either way, it’s highly unlikely that you’ll find a band-aid to cover up this problem. Address this issue right away or it can worsen quickly!

How to fix white smoke

Intake Gaskets

You’ll first want to inspect the intake gaskets to see if there is any leaking or rust.  This is the area where the manifold and head unite. You’ll want to check the port within the cylinder head because if the coolant is getting mixed in with the air and fuel in the combustion chamber then you will definitely be seeing white smoke released from the exhaust.

If there is no leaking or rust then you can move on.

Examine the Head Gasket

This is the film going around the perimeter of the cylinder head that seals the head with the block.  If it is worn beyond repair, you’ll typically see parts of the gasket that are caked onto the block and other areas are completely missing as if it has been melted off or cut out.  Either way, it’s not good.

You’ll want to immediately replace the head gasket, but you’ll also want to look for any cracks in the cylinder head which is made of aluminum and overheating can cause it to easily crack.

Check for Cracks in the Cylinder Head

The cylinder head is the part that connects the engine block with the head gasket.  If you checked the intake gaskets and the head gasket and both looked like they were intact, then the next step would be to check the head.

Unfortunately if the cylinder head is damaged or cracked in any way then it must be replaced.  During engine use it is very vulnerable to overheating and cracks will continue to spread making it very dangerous to use.  

The Good, The Bad and The Ugly

Smoke coming from your exhaust doesn’t necessarily mean a problem, it can represent the burning of naturally occurring condensation, but that doesn’t mean that all smoke is benign.  Black smoke means an overly rich fuel mixture and white smoke could mean as much as a cracked cylinder head. Go through the proper checks before jumping to drastic conclusions.

It’s been my intention to make this post as informative as possible about why your ATV might be releasing smoke from the exhaust.  If you have questions, feel free to comment below.

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