How to Clean the Carburator of Your Chainsaw – Not As Hard As You Think

Cleaning the carburator of your chainsaw can be the difference between throwing a saw away and having it run like new. It’s not that hard to do.

This guide walks you through the process of cleaning the carburetor on Stihl chainsaw models MS 290, MS 310, MS 390, 029, and 039. A clogged carburetor is often the culprit behind poor engine performance, difficulty starting, and rough idling. This moderate-difficulty maintenance task takes approximately 30-45 minutes and can save you hundreds in repair costs while extending the life of your chainsaw. Regular carburetor cleaning ensures optimal fuel efficiency and consistent power when cutting.

The video shows the process. I don’t know what’s going on with the first 9 minutes of the video, or what’s up with the mechanic character. All I can say is the technique worked great.

This video is specific to a chainsaw that I own (the Stihl MS 290, from about 2008). If you don’t own one of the models specified, you might need a different video, but this one will give you an idea of the process in about 10 minutes.

Tools and Materials

Straight and Phillips screwdrivers
8mm or 5/16″ socket wrench
Carburetor cleaner spray
Compressed air source (low pressure)
Small container for screws and parts
Clean rags or shop towels
Carburetor rebuild kit (optional, if parts need replacement)
Heat gun (optional, for throttle linkage adjustment)

Preparation

Before beginning, ensure you’re working in a well-ventilated area away from any open flames or heat sources. Wear safety glasses to protect your eyes from cleaning solvents and debris. Lay down a clean work surface to organize parts as you disassemble the carburetor. Empty ALL fuel from the chainsaw’s gas tank to prevent spillage and potential fire hazards during disassembly. Allow the saw to cool completely if it has been running recently.

Safety Warning: Always disconnect the spark plug wire before performing any maintenance on your chainsaw to prevent accidental starting. Gasoline is highly flammable – work in a well-ventilated area away from ignition sources.

Step By Step

Empty the gas tank completely to prevent fuel spillage during carburetor removal.
Safety Warning: Failure to empty the tank may result in fuel spraying out under pressure when fuel lines are disconnected.
Remove the top cover of the chainsaw to access the air filter and carburetor assembly.
Note the position of the climate control shutter (marked with sun/snowflake symbols). This controls airflow for summer or winter operation. Set it to the appropriate setting when reassembling.
Pro Tip: The snowflake setting allows heated air from the engine for winter operation, while the sun setting is for normal temperatures. Using the correct setting for your climate improves starting and performance.
Remove the air filter and set aside. Squeeze the throttle trigger and use a screwdriver to pop out the throttle linkage clip that connects to the carburetor.
Using your 8mm or 5/16″ socket, remove the two mounting nuts that secure the carburetor to the engine. Note the orientation of the mounting flange.
Pull the carburetor straight back away from the engine. Disconnect the fuel line by gently prying it off with a screwdriver or your finger.
Pro Tip: Take photos during disassembly to help remember the correct orientation of parts during reassembly.
Identify the two sides of the carburetor: the fuel pump side and the diaphragm side. First, examine the fuel pump side for debris.
Remove the cover on the fuel pump side and inspect the small pocket and screen inside. Clean out any sawdust or debris using carburetor cleaner.
Carefully clean the screen using carburetor cleaner. If the screen is removable in your model, you can take it out for more thorough cleaning.
Use low-pressure compressed air to gently blow out any remaining debris. High pressure can damage the delicate components.
Remove the cover on the diaphragm side using a Phillips screwdriver. Inspect for any broken sealant that may be clogging the main jet.
Check that the diaphragm is soft and supple. Examine the fuel pump flappers for damage. Replace with parts from a rebuild kit if any components show signs of wear or damage.
Clean all parts thoroughly and reassemble the carburetor, ensuring all gaskets and diaphragms are properly aligned.
Reinstall the carburetor. Ensure the connecting rod slips into its designated slot.
Reattach the throttle lever by inserting the tab and snapping it back into place. The tab must sit on top of its mounting point.
Align the carburetor with the mounting studs, making sure the flanges face outward, and secure with the mounting nuts.
Reconnect the throttle linkage by fishing it through from the inside out. Squeeze the throttle trigger to create space and pop the linkage back into place.
Reinstall the air filter and top cover, setting the climate control to the appropriate season setting.
Refill with fresh fuel, then start your saw.

Troubleshooting

If your chainsaw still doesn’t run properly after cleaning the carburetor, consider these common issues:

Engine starts but dies immediately: Check the idle adjustment screw. If your saw has adjustment screws accessible from the outside of the carburetor, try turning the idle screw clockwise in small increments until the saw idles smoothly.

Throttle linkage keeps popping out: The spring tension may be insufficient. Use a heat gun to carefully warm the plastic throttle lever, then gently pinch the mounting point to create a tighter fit.

Engine runs rough at full throttle: The high-speed mixture may need adjustment, or there could be an air leak between the carburetor and engine. Check that all gaskets are intact and mounting nuts are tight.

Saw continues to flood: The needle valve may be stuck or damaged. Consider replacing the complete carburetor assembly or having it professionally serviced.

Fuel leakage: Check all fuel line connections and the condition of the fuel lines themselves. Replace any cracked or brittle fuel lines immediately.

Additional Considerations

In humid climates, carburetors tend to accumulate moisture which can lead to more frequent clogging issues. Consider using fuel stabilizer and always drain the fuel system completely if storing your chainsaw for more than a month. For cold weather operation, always use the snowflake setting on your climate control shutter to prevent carburetor icing.

While cleaning is often sufficient to restore performance, a complete rebuild kit typically costs between $15-30 and provides new gaskets, diaphragms, needle valves, and screens. This can be a cost-effective alternative to purchasing a new carburetor assembly ($60-100) or taking your saw to a repair shop ($80-150 for service).

Consider pairing this maintenance with air filter cleaning and spark plug replacement for comprehensive engine care. If you find this procedure helpful, you might also want to learn how to sharpen your chainsaw chain and adjust the chain tension properly – both crucial maintenance tasks that improve cutting performance and safety.

If the video above moves to quickly, here’s another one that doesn’t.