Why Is My Chainsaw Bogging Down? (3 Common Causes)

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Working outdoors can be such a cathartic experience. However, when your chainsaw bogs down, it turns your enjoyable day in the backyard into a complete headache.

Your chainsaw bogging down is a common issue that you’ll face when wielding one, and it can quite quickly throw a knot in your woodworking projects. This handy guide will cover the common problems that cause bog down and how you can keep it from happening in the future.

What Causes My Chainsaw to Bog Down?

Unless you are running an electric chainsaw (which is a totally different beast), your chainsaw’s motor is a combustion system that relies on a proper ratio of gas, oil, and air. If your chainsaw is bogging down, one of these critical components isn’t in its correct balance.

There’s a myriad of issues that can lead to a bogged-down chainsaw, and most of them have something to do with your chainsaw’s combustion engine’s ability to access fuel or air amply. If your chainsaw cannot get enough of either one of those critical components, it will cause the motor to stall.

The most frequently seen causes are:

• Improperly mixed fuel
• Blocked air filter
• Filthy carburetor

Improperly Mixed Fuel

If your chainsaw is bogging down when you press the throttle, it can be a sure sign of an incorrect gas-to-oil ratio. A “rich mixture” occurs when you have too much gasoline with the amount of oil in your fuel mixture, resulting in a poorly operating chainsaw.

How do you know what the best gas-to-oil mixture is the best for your chainsaw? The answer is simple; you check your chainsaw’s owner’s manual. The manual should give you the proper gas-to-oil ratio for your particular chainsaw.

The majority of chainsaws operate on one of the three following gas-to-oil mixtures:

• 30:1
• 40:1
• 50:1

If you have already mistakenly filled your chainsaw with the wrong fuel mixture, you will need to drain the incorrect fuel and replace it with the right mix.

Now that you know how incorrectly mixed fuel can impact your chainsaw, it’s time to learn the correct way to combine the right fuel you need to get your motor up and running!

How to Properly Mix Fuel for Your Chainsaw

Knowing how to mix fuel properly is the first step to ensuring that your chainsaw will stay up and running for years to come. The proper fuel mixture is essential for effective, trouble-free operation.

First, you’ll need to pull out your reading glasses and take a look at your chainsaw’s owner’s manual. As mentioned before, most chainsaws will run on one of three gas and two-cycle engine oil mixtures.

Next, you’ll need to gather the right supplies for the job at hand. You should use mid-grade unleaded gasoline with a minimum octane rating of 89 and a premium two-cycle oil.

Lastly, it’s time to play mixologist. You cannot mix oil and gas directly in your chainsaw’s fuel tank and will need an empty, leak-proof fuel container that is just slightly larger than the volume of oil and gas being mixed.

Follow these simple steps to become a master fuel mixologist:

1. Add your pre-measured oil to the container
2. Add your pre-measured gasoline AFTER (not before) your oil
3. Seal your fuel container and swirl, not shake, to thoroughly combine the oil and gasoline
4. Once properly mixed, your gas and oil mixture will be evenly colored with no variegated streaks

You can now correctly mix the gasoline and oil needed for your chainsaw, so let’s move on to other issues that can arise and cause a bogged-down chainsaw.

How a Blocked or Dirty Air Filter Can Cause Your Chainsaw to Bog Down

Suppose that your chainsaw’s fuel mixture is correct, and you’re still experiencing a lag in performance. In that case, it’s best to check your air filter and clean it if needed before moving on to more complex issues.

The air supply is just as important as a fuel supply in any internal combustion engine. All internal or external factors that reduce the supply of combustible air causes bogging down. This is partly due to clogged filters resulting from long working hours and less air supply to the carburetor (which will be discussed later).

How to Clean the Air Filter on Your Chainsaw

Cleaning your chainsaw’s air filter can lead to an improvement in performance and really should be done as part of your routine chainsaw maintenance schedule. You can follow these simple steps to remove and clean your chainsaw’s air filter:

• Check your owner’s manual to locate your chainsaw’s air filter
• Remove the chainsaw’s top cover
• Dismantle the spark plug boot for safety
• Your chainsaw’s air filter should be visible at this point and can be easily removed from its housing with a screwdriver
• After removing the air filter, wash it in soapy water and scrub with a soft-bristle brush until clean
• Allow your air filter to dry thoroughly before replacing it in your chainsaw

You should note that if your air filter continues to look dirty after cleaning and drying, it is time to fully replace the air filter with a new unit.

If you’ve checked both the fuel mixture and air filter on your chainsaw and still experience bog down, it may be time to move on to the carburetor.

How Carburetor Issues Can Bog Down Your Chainsaw

A carburetor is a part of a combustion motor that mixes air and fuel in a specific ratio for combustion. If any part of that ratio is off (as previously mentioned), your chainsaw will experience a lag in performance.

If your chainsaw’s carburetor becomes clogged with dirt and debris, airflow is restricted and the chainsaw’s engine suffers. Other indicators that your chainsaw may be suffering from carburetor troubles are overheating or excessively smoky exhaust.

You can clean clogged or dirty carburetors with carburetor-specific cleaning solutions that you can purchase at your local chainsaw dealer or auto parts store.

If your chainsaw’s carburetor is not clogged, the tuning of your carburetor may be to blame. Most manufacturers do not recommend adjusting the tuning of your chainsaw’s carburetor outside the hands of a trained professional. Still, if you feel that you can do so yourself, you can watch this YouTube tutorial here.

Simple Maintenance Can Prevent Bogging in Your Chainsaw

Poor chainsaw maintenance is one of the lead causes of bogging. To keep your chainsaw running smoothly, you should service it regularly and keep up scheduled maintenance visits with a reputable, authorized chainsaw service center.

Here’s a quick rundown of daily, weekly, and monthly maintenance tips:

Daily	Weekly	Monthly
Always clean the outside of your chainsaw after using it to remove any dust or debris that may be present.	Check that the anti-vibration elements are not damaged, torn, or soft.	Check the brake band for wear and tear. If the band is measuring less than 0.6 mm (0.024 in) at the most worn part, you need to replace the brake band.
Thoroughly inspect your throttle trigger. If binding/catching occurs, or if the motor does not return to an idle state, your chainsaw needs to make a visit to a service provider before being used again.	Run a check on your chainsaw’s cooling system.	Inspect the clutch center, drum, and spring for any excessive wear.
Clean and check the function of your chain brake.	Inspect and oil the clutch drum bearing.	Clean the outside area of the carburetor.
Check, clean, and replace (if necessary) the air filter.	Check the edges of the bar for burs and file off if needed.	Check inside the fuel tank for dirt and debris. Empty and clean, if needed.
Turn your chainsaw’s bar to ensure even wear and tear. Also, check the lubrication hole for debris and clean your bar groove.	Clean your spark plug and measure the gap. It should measure at 0.5 mm (0.20 in)	Inspect and clean the oil tank.
Be sure that your oiler is adequately lubricating your bar and chain.	Clean and/or replace the spark arrestor screen.	Look over all cables, connections, nuts, and screws to ensure that they are not damaged and need replacement.
Check the tension and condition of your chain.	Clean flywheel fins.	Sharpen your chain’s cutting teeth.
Clean air intake slots on the housing of the starter and inspect your starter cord for any damage.	Check the return/recoil spring and starter.	File the chain’s depth gauges.
Check for any loosened nuts or screws and retighten if needed.	Check cooling fins on the cylinder and clean if needed.
Test your stop switch to make sure that it completely stops the motor.	Inspect and clean the airbox.
Check for any fuel leaks from the motor, fuel tank, or fuel lines.	Clean carburetor body.

How to Check and Adjust the Chain Tension on Your Chainsaw Chain

Chains will loosen over time and use. It’s an essential step in properly maintaining your chainsaw to check and adjust the chain tension.

Here’s a quick rundown of how to do just that:

1. Make sure that your chainsaw is off and cool (Heat isn’t your friend here!)
2. Release the chain brake
3. Using a specialty tool called a scrench or a combination wrench, loosen the bar nuts holding the clutch cover in place
4. Tighten the chain tensioning screw using your combination wrench or scrench while raising the tip of the bar and stretching the chain.
5. Continue to tighten the chain until there is no slack on the underside of the bar, but it can still be freely pulled by hand
6. Tighten the bar nuts, return the clutch cover to its rightful place, and ensure that the bar is secure

How to Sharpen the Cutting Teeth on Your Chainsaw Chain

Keeping your chainsaw chain sharpened will enable you to keep cutting with precision and efficiency. You will also reduce kickbacks and increase the overall safety of operating your chainsaw.

You will need to use a file to sharpen your blades monthly or when the debris left from your saw cuts is more dust and fewer wood chips. Chain filing isn’t a difficult task and is crucial in maintaining your chainsaw.

To sharpen the cutting teeth on your chainsaw chain, follow these easy steps:

1. You will need a round file that matches the diameter of your cutters, a flat file, a file guide, and a depth-gauge guide.
2. Secure your chainsaw to maintain stability while working. This can be done with a vise, clamps, or any type of fastener that will stabilize your chainsaw.
3. Lock the chain brake by pushing the handle forward. This will keep your chain in place for the next steps.
4. Mark the starting point of your filing.
5. Start by sharpening the cutting teeth of the blade first. You will need to position your file depth gauge so that the arrows are pointing toward the nose of the chainsaw bar.
6. File every other cutting tooth with smooth, even, pushing strokes, keeping the round file at a 90-degree (right angle) to the rollers.
7. Disengage the chain brake and manually advance through the chain until you reach your starting point mark.
8. Rotate the saw and file the remaining teeth using the same angle and motions as before.

If you are not comfortable sharpening your own chains, be sure to take your chainsaw to a reputable service provider and have it professionally done.

Simple Maintenance That You Should Follow Every Time You Use Your Chainsaw

Before tossing your chainsaw in the shed, there are a few simple things you should do to ensure the longevity and productivity of your tool. The majority of these steps are listed above in the daily maintenance list, but one is of top priority:

• Clean your chainsaw. Clear all dirt and debris from the saw body, chain, and bar. Do not store a dirty chainsaw.

Final Thoughts

Chainsaws require maintenance to stay at the top of their game. If you’re finding your chainsaw to be bogging down, check the issues mentioned above to see if you can save yourself a little time and money.

Don’t forget that a maintained chainsaw is a working chainsaw!

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