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Chainsaw Keeps Bogging Down? Here’s What to Do


Chainsaw bogging down: causes and how to fix it.

A bogged-down chainsaw is one of the most common issues you can come across when working with one, and it can quickly put a delay on woodworking projects. Several different factors can cause this issue, but it’s usually easy enough to fix. 

The most common causes of a chainsaw bogging down include:

  • Incorrect fuel mixture
  • Dirty carburetor
  • Clogged air filter
  • Dirty fuel filter or fuel lines

A combustion system depends on a proper mix of gas, oil, and air. One of these is not being fed to the chainsaw in the proper ratio. Find the source of the issue and you can easily fix it. Read on to learn more about what causes a chainsaw to bog down and how to repair it. 

Causes of a Bogged Down Chainsaw

Several potential causes may lead to a chainsaw bogging down. Many of them have to do with the combustion engine’s ability to access either air or fuel. If the chainsaw can’t get enough of either, then this can cause the chainsaw to stall. 

Incorrect Fuel Mixture

If your chainsaw is bogging down when you give it throttle, this is often a sign of improper gas-to-oil ratio. If there is too much gasoline in relation to the amount of oil used, this is known as a “rich mixture” and can cause the chainsaw to run poorly. 

So how do you determine what the correct mixture of fuel is for your chainsaw? The answer is in your operator’s manual. You should be able to find the appropriate ratio of gas to oil you should be using. Most chainsaws operate on the following gas-to-oil ratios:

  • 30:1
  • 40:1
  • 50:1

If you’ve already filled your chainsaw up with an improper mixture of fuel, you’ll need to siphon the fuel out and replace it with the correct mixture. The best gasoline for a chainsaw is mid-grade gasoline with an octane rating of at least 89. When making a fuel mix for a chainsaw, be sure to mix the gasoline into the oil, and not the other way around. (Source: Hunker)

Carburetor Problems

Another issue you can run into when your chainsaw is bogged down is carburetor problems. The carburetor is the part of the chainsaw’s engine which calibrates the mixture of fuel and oil to air in the combustion system. When the carburetor becomes clogged with debris, this prevents enough air from moving through the carburetor to keep the chainsaw’s engine running. 

Some other symptoms that you might run into with a clogged carburetor along with bogging down include things like smoking exhaust or overheating. If you run into a carburetor issue that causes the chainsaw to overheat as well as bog down, you should repair the chainsaw quickly to prevent permanent damage to the engine. 

Carburetors that are clogged with corrosion from use can be cleaned with a carburetor cleaning solution. If the carburetor is not clogged, the other issue that could cause a carburetor to bog a chainsaw is the tuning. Tuning the carburetor by adjusting either the idle speed, the low-speed, or the high-speed screw adjustments. 

If the idle screw is turned up too low, the chainsaw will lose power whenever the throttle is released. Turning the low-speed fuel adjustment screw to reduce the richness of the fuel/air mixture can also help to prevent bogging issues. The high-speed fuel adjustment screw is turned down to reduce fuel richness if bogging is a problem. All of these adjustments help improve the air/fuel mixture in the engine. 

Clogged Air Filter

Many chainsaw operators first notice a problem with chainsaws bogging down when they’re using the chainsaw under load, and this is usually the result of poor air circulation. This issue is caused by a clogged air filter on the chainsaw.

Note: This YouTube video gives an excellent overview on removing and replacing an air filter in a chainsaw:

Replacing the Air Filter - Husqvarna Chainsaw
  • Remove the air filter from the chainsaw. If you aren’t sure where the air filter is located, check your chainsaw’s operating manual.
  • Remove the top cover of the chainsaw and remove the spark plug boot for safety. The air filter should be visible and you should be able to remove it from its housing with a screwdriver.
  • Wash the air filter in soapy water until the air filter comes completely clean. The air filter can also be scrubbed with a soft brush to remove any clinging particles. If the air filter still looks dirty even after washing it, this is an indication that the air filter needs replacement.
  • Remove the spark arrestor. This is a small screen located behind the muffler cover on the chainsaw. The spark arrestor can be scrubbed gently clean with a wire brush to remove any corrosion or debris.  

If you’re trying to troubleshoot a bogging chainsaw, it’s a good idea to check the air filter and clean it if necessary before you start messing with the fuel adjustment screws on the carburetor. Many chainsaw manuals discourage adjusting the carburetor 

Maintenance and Chainsaw Bogging

Often when a chainsaw ends up with a bogging problem, it’s a result of poor maintenance on the machine. Taking care of a chainsaw before and after use and inspecting its different components for wear and tear throughout the season can help you identify potential problems before they become serious enough to cause permanent engine damage or cause it to stall completely. 

Here are some ways to keep your chainsaw maintained to prevent issues with bogging: 

  • Clean your chainsaw. One of the biggest problems with chainsaws that can damage their mechanisms or engine is the build-up of sawdust and other debris during the process of running in the cut. Cleaning your chainsaw before and after each operation thoroughly can help prevent the build-up that leads to clogged air filters and carburetors. 
  • Use new or stabilized gas. As a general rule, you shouldn’t use gas that has been stored in a chainsaw’s gas tank for more than 30 days unless you’ve added a fuel stabilizer (link to Amazon). Stabilizers are designed to help keep fuel stable and fresh for months. 
  • Lubricate your chain. Lack of lubrication can cause a chainsaw to work harder than it needs to because of added friction and heat, and this, in turn, can cause bogging. Left unchecked, overheating related to friction can stall a chainsaw or damage it. Keeping your chainsaw lubricated with chainsaw bar oil (link to Amazon) will make sure it cuts clean without stalling or overheating. 
  • Sharpen the blades. Running a dull chainsaw is the quickest way to wear out the motor and cause undue wear and tear to the rest of the chainsaw as well. Chainsaw blades can be sharpened with a metal file at home, or you can take your chainsaw to a small engine repair shop to have it sharpened there. 

Keeping up with your chainsaw’s maintenance each time you use it can significantly increase the lifespan of your machine. Since chainsaws aren’t exactly cheap, it’s worth it to take the time to keep the engine cared for both during and between uses. 

Chainsaw Bogging Can Be Fixed at Home

If you find yourself in a position where your chainsaw just doesn’t have the power it should, try doing a little troubleshooting before you take it to a small engine repair shop. Chances are, with just a little patience, you should be able to correct most bogging issues easily at home. 

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Teddy Henderson

Teddy is always fiddling with small engines, picking up thrown-out string trimmers or tearing apart dirt bikes. He shares what he learns along the way. Hopefully, you'll have less headaches than he has had by learning from his mistakes.

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