How to Tune a Chainsaw Carburetor

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In a recent blog I referenced the Game of Logging courses I attended and described all the new things I learned about safe and efficient use of a chainsaw. One such item was chainsaw maintenance, and one part of that was the carburetor test. I’ve run chainsaws for over 30 years and never knew to how adjust the carburetor. If you have a new saw, this won’t apply to you, as new regulations require saws to be built so that only a qualified technician can tune the carburetor. However, if you have an older saw, here’s how to quickly tune it yourself. Start by locating the three adjustment screws. They are typically labeled L (low speed jet), H (high speed jet), and I (idler jet). Your saw may be labeled differently (in the photos in the Gallery below, the idler jet is labeled “S”), but you’ll have three screws that correspond to these descriptions. Search your owner’s manual for guidance on how to adjust the carburetor.

Note: Your owner’s manual may advise you not to adjust the carburetor without a tachometer, which helps ensure you don’t run the engine too high. If you have a tachometer, great. If not, you can still follow the steps below to tune the carburetor, being careful not to rev the engine longer than suggested here.

Now, let’s tune your saw.

1. Start your saw and run it for a few minutes to warm it up.

2. Set your saw down, let it idle for 30 seconds, and then pick it up and tip it forward (handle up and bar down).

3. If it keeps running, go to Step 4. If it stalls, tighten the Low Speed screw. This will reduce the amount of fuel entering the carburetor. Repeat Step 2 as necessary.

4. Rev (accelerate) the idling saw.

5. If it accelerates fine, go to Step 6. If it “dogs,” loosen the Low Speed screw. This will increase the amount of fuel entering the carburetor. Repeat Step 4 as necessary.

6. Rev the idling saw for about 5 seconds (never rev it for 10 seconds or longer).

7. If it “flutters” while being revved, this is good, so go on to Step 8. If it “screams” while being revved, this is bad. Loosen the High Speed screw. Repeat Step 6 as necessary.

8. If the chain is stationary while the saw idles, you’re finished.

9. If the chain rotates around the bar while the saw is idling, adjust the Idler Screw as necessary to make it stop. This situation can be fixed in a matter of seconds and is extremely dangerous if not corrected.

That’s it. Less than five minutes of your time can make a big difference in how well your saw runs. Two additional tips are 1) use hot water and dish soap to clean a paper-type air filter (let it dry before using), and 2) use chainsaw gas to clean a wire-type air filter (you don’t need to let it dry before using).

This information will help your saw run more effectively and efficiently. This will allow your saw to last longer, and it will require less force and labor on your part. Collectively these equate to safer operating conditions and more seasons in the deer stand for you.