My Chainsaw Bogs Down When I Give it Gas: Why?

From falling trees to slicing timber, the chainsaw is a necessity –  especially if you are in the lumber industry. The last thing anyone wants is a saw that purrs when idling and bogs down when applying gas.

There are several factors may make your saw not work properly. 

First, it could be that the carburetor, spark arrestor or the air filter are dirty.

Or, the carburetor adjustment might have simply slipped.

This guide will explore some of the reasons why you chainsaw bogs down as well as the different ways to fix it.

Reasons Why Your Chainsaw Bogs Down

High-Speed Screw

When the high-speed screw in the carburetor isn’t adjusted properly or is open too far, excess air will enter the combustion chamber, and not all of it will ignite. Apart from the poor cutting performance, not all fuel in the saw will burn and this produces smoke which fills the air filter and sparks plug causing performance issues.

To mitigate such an issue, you should ensure that the screw is closed but not too far from the engine as it could lead to more serious problems.

Sometimes when the mixture in the engine becomes too lean the engine tends to overheat and races which can cause the piston to seize. It can prove difficult to get the right high-speed adjustment by ear, and it’s best if you use a tachometer.


Before making adjustments to your carburetor’s high-speed screw which is highly discouraged by most chainsaw manufacturers you should clean the spark arrestor and air filter.

If any of these are dirty, then chances are they are contributing to your chainsaw stalling and you should thoroughly clean them.

Begin by removing the filter then wash it with soapy water or blow it with compressor air.  If you still can see dirt, then you should consider replacing it.

Chainsaws are designed differently, but most spark arrestors are located behind the muffler. You should pull it out after removing the muffler cover and clean it properly using a wire brush.

Clean The Spark Plug

One of the essential aspects of diagnosis of engine bogging is to remove and take a closer look at the spark plug.

If you realize that the plug is coated with carbon deposits, then it’s a sign that the fuel mixture within the combustion chamber is too rich. If this is the case, then you’ll also find excess deposits on the spark arrestor.

Adjust The Carburetor

On most newer chainsaw models it is difficult to regulate the volume of fuel that the carburetor passes to the combustion chamber.

If in any case, the engine stops while idling then the idle adjustment should be tightened. If your engine doesn’t bog until you depress the throttle, you should either tighten the high or low-speed adjustment screw to enhance its performance.

Take a look at this video I found helpful from Foxboss9 on YouTube:

Keeping all these factors in mind, you should be able to diagnose your chainsaw the next time it stalls.