Chainsaw Bogs Down

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Written By Janine Clarke

I am Janine Clarke AKA Equipment Girl, a nerdy girl with an unhealthy knowledge about power tools and gardening! You can contact me here.

Woodworking projects are fun, more a fun pastime than a chore for most. But when you’re in the middle of your project and your chainsaw bogs down, it can become a real problem.

Chainsaws bogging down is never a good situation to be in, especially at high speed with the chainsaw chain halfway through a large piece of wood just to have the chainsaw’s engine start messing up, spluttering, and potentially cutting out.

So what causes chainsaw bogging? How can you fix it? And what can you do in the future to prevent it from happening again? Well, read on below and you’ll find out all that and more!

What Does It Mean When Your Chainsaw Bogs Down?

It’s difficult to describe what a chainsaw bogging down feels like, because it can be different for everybody depending on the cause of the issue, and how bad that issue is.

With that said, there are a few symptoms/things to look out for to suggest that your chainsaw is bogging down:

  • Engine sounds – if the engine begins to sputter or sound as if it is losing power, then this is a sign of a bogging chainsaw.
  • Engine starts and then cuts – if the engine starts and stops, cutting out, restarting, etc., then your chainsaw is bogged down and there’s a problem.
  • Low speed – if the chainsaw is cutting fine initially, but eventually reaches a low speed where it’s no longer able to cut through the wood, then it’s bogging down.

Basically, if your chainsaw seems low on power, low on speed, sounds different, or starts and stops different from before, then it’s bogging down, and it can be caused by one of four things…

Causes Of A Bogged Down Chainsaw

Before we look at the best ways of fixing a bogged down chainsaw, let’s focus on the four main causes. The key areas of your chainsaw you’ll want to focus on now are the carburetor, air filters, fuel tank, and fuel mixture.

Dirty Carburetor

Your carburetor is the main part of the engine responsible for mixing the air and fuel mixture in a proper ratio for combustion in the combustion chamber. If the ratio isn’t right, because there’s too much gasoline or too much air, then this can cause the chainsaw to bog, because chainsaws operate best when the oil mixture for combustion is just so.

If the carburetor is dirty due to debris or corrosion, then it will need to be cleaned properly to allow the fuel/air supply into the combustion chamber so it can perform consistently instead of cutting out.

Consider Misalignment Too

It isn’t just dirt that can affect a carburetor either. If the carburetor isn’t tuned properly, then you’ll notice issues too.

A carburetor adjustment might be in order, but sometimes a carburetor adjustment is best left to the professionals. If you feel you are capable, though, then you’ll need to check the idle screw, low-speed screw, and high-speed screw to ensure they are properly aligned.

These three adjustment screws control the way your chainsaw acts during idle speed, low and high speed. If they aren’t correct, then your chainsaw’s performance will be affected.

To adjust the screws in the carburetor yourself, consider consulting a professional, or at least watching videos online and reading the owner’s manual to get comfortable with the process before doing it yourself. The high-speed screw in particular could cause issues and potentially a serious injury if it isn’t adjusted properly.

Dirty Air Filter

Dirt in your air filters is actually one of the leading causes of a chainsaw bog, because air can’t pass through the air filter effectively when it’s blocked by debris and dirt.

You’ll notice problems here when the chainsaw is at full throttle, and the saw itself stutters, because the huge amount of air required in the combustion system when at full throttle just can’t get through the clogged air filter.

If you notice poor performance at high speed, check that your chainsaw doesn’t have poor air circulation due to a clogged air filter.

Dirty Fuel Lines/Fuel Filter

As you’re probably starting to see, the correct mixture of air and fuel is vital for a chainsaw’s performance. If there is dirt in the line and filter in the fuel tank, then there can be problems.

Fuel, air, and dirt is an improper mixture. Your chainsaw engine won’t know how to deal with this type of fuel mix, so it’s important to make sure you’re not using old or dirty fuel. If dirt has been allowed to accumulate in the tank, lines, and filters, then it will cause the chainsaw to bog down.

A Note On Your Spark Arrestor/Spark plug

Similarly, if dirt is allowed to affect the spark plug or spark arrestor, you’ll notice problems. The spark plug and spark arrestor in the engine is designed to help the chainsaw start. The two work together to create a spark that lights the fuel mixture which causes the combustion which powers the chainsaw. If spark plugs or a spark arrestor are allowed to get dirty, it can’t light the fuel to begin with or keep it burning right.

Incorrect Fuel Mixture

Talking of fuel, it may be that the mixture just isn’t right. This is most notable when you press the throttle. If the issue starts right away, then it’s likely that the ratio isn’t right for oil, and gas.

Most chainsaws actually require different ratios of gas to oil, but if you use a mixture with too much gas compared to oil, then this is known as a ‘rich mixture’, and your chainsaw won’t be able to operate successfully. You can find out what ratio is right for your specific model of chainsaw by checking the user manual.

How To Fix Chainsaw Bogging

Now you know the main issues, let’s talk about the solutions. It’s actually not unreasonable to do all of the steps below to ensure you fix the issue, because the cause may be all four in combination with one another.

A chainsaw maintained properly will always perform well, so try each step below to fix your bogged down chainsaw issues and get it back to working order.

Properly Mixing Your Fuel

As mentioned above, the first thing you need to do is make sure your gas-oil mix is correct – this can be found in the owner’s manual.

Typically, your gas to oil mixture will be either 30:1, 40:1, or 50:1 – too much oil, and your chainsaw bogs down.

If you notice that you’ve used the wrong mixture, unfortunately you’ll have to drain it. After that, it’s time to mix your oil and gas with the right ratio for your chainsaw – again, make sure you read your user manual for this, or else you’ll get the wrong mix again.


  • Take a fuel container (you shouldn’t mix in your chainsaw’s fuel tank – a separate container first is key) and add the correct amount of oil into it.
  • Next, add your gas – the right amount.
  • Then close the lid of the container, ensuring it’s sealed tight, and swirl the mixture to properly combine it.
  • Pour the mix from the container into the chainsaw tank.

If you follow these steps and improper fuel mix was the cause of your bogging issues, the chainsaw should now run normally.

Cleaning Your Fuel Lines

If the cause was a dirty line, filter, or tank, you’ll need to clean this before adding new fuel.

The best way to clean out your tank in general is with soapy water – it’s a simple fix, but it will remove any dirt and debris that’s ruining your fuel mix.

Pour hot soapy water into the tank to allow it to clean the filters and lines, swishing the mix around a little to help get all the debris. Pour out the contents, rinse with just hot water until all soap is gone, then pour out and leave the whole tank to dry fully (around 24 hours) before attempting to add any more fuel again.

Cleaning Your Air Filter

If the air filter is the issue, then here’s what you’ll need to do.

Locate your air filter by looking at your manual’s diagram first. Remove the chainsaw top cover, dismantle the spark plug boot for safety and clean or replace the spark arrestor screen (a small screen behind the muffler cover) if this is dirty too.

Once the spark plug boot has been dismantled, you’ll notice your air filter. An air filter can be removed with a screwdriver. Clean your air filter with soapy water and a soft wire brush if it’s particularly bad, or simply use compressed air to remove any other debris.

If wet, allow the air filter to dry fully before replacing it in the engine again.

Cleaning Your Carburetor

Cleaning your carburetor is very easy. If excess fuel enters the combustion chamber because the high-speed screw is open too far, cleaning will almost certainly be necessary to remove the buildup.

Note: We won’t cover how to adjust the three screws in your carburetor today, so if this is necessary, watch videos online or consult a professional.

To clean your carburetor, though, all you need to do is buy a carburetor cleaning solution from a hardware store, and use it per the package instructions to remove buildup, dirt, or debris. A soft wire brush can help remove the worst of the dirt.

Maintenance Prevention

Poor maintenance is usually the cause of your chainsaws bogging down. When your chainsaw ends up with bogging issues, it’s almost always avoidable, so once you’ve fixed the issue today, be sure to keep up with a maintenance schedule to avoid the same issues recurring.

To finish, here’s what you should be doing regularly to avoid chainsaw bogging problems:

Clean Your Chainsaw

Keep up with regular cleaning, ensuring air filters, fuel lines, your spark plugs/arrestor and carburetor are all clean and ready to perform as they should.

New Fuel

New, stabilised gas is essential when using your chain saw. Fuel that’s been left in the chainsaw tank for more than 30 days should be discarded and a new mix should be made.


Finally, lubricating your chainsaw regularly will allow the blade to cut as it should, so there’s no unnecessary heat or friction, which can cause bogging down too.