If this is a sudden occurrence I think there is an air leak and the saw is running lean. Continued operation while lean or tweaking the needle valve to compensate may destroy your saw.
If you have more questions or need additional help please reply below and I will get back to you. HTH & Good Luck. Lou Thank You for using FixYa.
Check the fuel filter, air cleaner, and muffler for plugging. Does the engine have fresh fuel mix? The idle speed screw may need to be adjusted CCW somewhat until the chain ceases to move at idle. Have the H and L jet screws been adjusted? If so, turn both screws CW to stops (lightly), then both turned CCW 1-1/2 turns each. Start the engine and allow to warm up. Open the throttle and turn H CW until the engine speeds up, yet continues to 4-stroke. Proper setting is when the engine 4-strokes, yet immediately 2-strokes when cutting. Let idle, and adjust L until the engine runs fairly smoothly, but will allow the engine to 'follow the throttle'. Hope this helps!
Answers & Comments
If this is a sudden occurrence I think there is an air leak and the saw is running lean. Continued operation while lean or tweaking the needle valve to compensate may destroy your saw.
If you have more questions or need additional help please reply below and I will get back to you. HTH & Good Luck.
Lou
Thank You for using FixYa.
Check the fuel filter, air cleaner, and muffler for plugging. Does the engine have fresh fuel mix? The idle speed screw may need to be adjusted CCW somewhat until the chain ceases to move at idle. Have the H and L jet screws been adjusted? If so, turn both screws CW to stops (lightly), then both turned CCW 1-1/2 turns each. Start the engine and allow to warm up. Open the throttle and turn H CW until the engine speeds up, yet continues to 4-stroke. Proper setting is when the engine 4-strokes, yet immediately 2-strokes when cutting. Let idle, and adjust L until the engine runs fairly smoothly, but will allow the engine to 'follow the throttle'. Hope this helps!