The carburettor regulates the fuel-air mixture on a Poulan chain saw. The optimal carburettor settings will produce a clean sounding engine that won’t die, move the chain while idling and will cut wood quickly. Poulan saws have three carburettor adjustment screws: idle adjustment screw, which sets the idle RPM; low-speed adjustment, which controls the fuel-air mixture while the saw is idling; and high-speed adjustment screw, which controls fuel-air mixture when the saw is cutting.
Remove and clean the air filter. Fill the saw's tank with at least a 1/2 tank of fresh fuel. Start the engine and allow it run for 2 to 3 minutes if it is cold.
Turn off the saw and locate three holes on the right side of the Poulan’s body, near the handle bar. The top hole provides access to the high-speed adjustment screw, the middle hole is for low-speed adjustment and the bottom hole is for idle speed.
Remove with a pair of pliers the carburettor limiter caps that cover the adjustment screws.
Start the saw and let it idle. Turn the idle adjustment screw (bottom hole) clockwise until the saw shuts down.
Turn the screw counter-clockwise 1/2 turn and restart the Poulan saw.
Listen to the idle sound and adjust the idle screw until the proper idle speed is attained. Set properly, the chain should not move while idling, and the engine should not die when throttled and should produce a slightly heavy, bubbling sound.
Restart the saw and let it idle. Set the low-speed adjustment, or blue screw, by turning it clockwise all the way in or until the engine surges or sounds choked on fuel with a high-pitched whine. Remember the position of the screw in this setting.
Adjust the low-speed adjustment screw counter-clockwise 1-1/4 turns until the engine starts making a heavy bubbling sound. Remember the position of the screw in this setting.
Slowly turn the low speed adjustment screw clockwise until the idle sounds the best and cleanest. This position should be roughly half way between the settings in Steps 1 and 2 that you were instructed to remember.
Recalibrate the idle speed screw because the gas and air mixture will have changed with the low-speed adjustment.
Hold down the saw’s throttle to its maximum speed. Set the high-speed adjustment, or red screw, by turning it clockwise until the engine produces a loud, clean whine. Remember the position of the screw in this setting.
Rev the throttle to its maximum again and adjust the screw counter-clockwise until it produces a rich, bubbling or sputtering sound. Remember the position of the screw in this setting.
Slowly turn the screw clockwise until the saw has a rougher sound to the engine. This position should be roughly half way between the settings you were instructed to remember from Steps 1 and 2 of this section.
Recalibrate the idle speed and low-speed adjustments because they again will have changed after setting the high-speed adjustment screw.
It is unwise to adjust the maximum throttle speed or high-speed adjustment screw clockwise without a tachometer. Increasing the engine’s maximum RPM speed above the factory settings will cause your engine to burn out very quickly. If in doubt about the high-speed adjustment screw, take it to a licensed Poulan chainsaw dealer and have them adjust it for you.
Always wear the proper personal protective equipment when working with saws.