How to Adjust the Fuel Mixture on My Poulan Pro Chain Saw

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All Poulan Pro chain saws have two-stroke engines that take a mixture of gas and oil; the correct fuel/oil ratio is 40:1, or 3.2 ounces of oil per gallon of gasoline. If the engine runs sluggishly or stalls, you may have to change the amount of fuel the carburetor sprays into the combustion chamber; you do this by turning adjustment screws on the side of the carburetor.

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Locating the Adjustment Screws

The carburetor is located just behind the air filter, which is under a cover attached to the top of the engine. Remove this cover with a T-27 screwdriver to access the adjustment screws, which are usually on the left side of the engine as viewed when holding the chain in front of you. You should see three screws, although two may be protected with plastic guards. The screw on top -- marked "T" -- is for adjusting the fuel mixture while the engine is idling. Of the two underneath it, the one on the left is for adjusting the mixture when the engine is running a low speed, and the one on the right is for making the same adjustment when the engine is running at high speed. All small engine carburetors have these three adjustment screws.

Adjusting the Idle

Clean the air filter before adjusting the carburetor fuel mixture because the mixture will be too rich if you do it with a dirty filter. Replace the filter, start the saw and turn the "T" screw counterclockwise to increase the fuel mixture and the idle speed; turning the screw counterclockwise decreases both. You've achieved the proper fuel mixture when the engine idles smoothly but the chain doesn't spin.

Other Carburetor Adjustments

The manufacturer doesn't recommend adjusting the low- and high-speed screws yourself, which is why the screws are protected with covers. In the manual that comes with the 220 Pro, Poulan recommends having all carburetor adjustments done by a technician. Despite that warning, it's usually safe to adjust the low-speed screw, although you'll have to pry off the cover to do it. A basic procedure is to start the saw, turn the screw clockwise until the engine begins to stall for lack of fuel, then back the screw off until the engine stalls because it has too much fuel. The ideal setting should be midway between these points.

You adjust the high-speed screw in the same way while keeping the throttle fully engaged, but misadjusting this screw can burn out the engine. Instead of making the adjustment yourself, take the saw to an authorized technician who can do the job properly, using a tachometer.

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