Jonsered chainsaws run on two-cycle engines, which complete all engine cycles in one crankshaft movement. Two-cycle (or two-stroke) Jonsered chainsaws use a mixture of oil and gasoline for fuel. To keep the fuel supply regulated, the carburetor needs to be adjusted occasionally. An engine that sputters or cuts out unexpectedly often needs a quick tweak to repair. Regular adjustment of the carburetor prevents unnecessary wear to the chainsaw's engine.
Locate the three adjustment screws on the carburetor. The "L" or low setting screw is at the bottom, the "H" or high speed screw is to the right, and the "T" or idle screw is to the left.
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Start the engine and allow it to run.
Turn the "L" screw counterclockwise to allow more fuel into the carburetor until the low setting runs smooth without sputtering.
Rotate the "T" screw counterclockwise, a 1/4-turn at a time, to even out the idle of the machine to prevent sputtering and cut out.
Turn the "H" screw clockwise until it won't turn any more then rotate it counterclockwise 1/4-turn. Press the trigger for the chainsaw to engage the high setting. If it sputters or cuts out, turn the "H" screw counterclockwise to increase the fuel supply.