9MS 311, MS 391
3.2 Chain Drive, Chain Brake, Chain Tensioner
Condition Cause Remedy
Chain sprocket wears rapidly Chain not properly tensioned Tension chain as specified
Wrong chain pitch Fit chain of correct pitch
Insufficient chain lubrication Check chain lubrication
Chain sprocket worn Fit new chain sprocket
Saw chain stops under load at full
throttle
Clutch shoes badly worn Install new clutch
Clutch drum badly worn Install new clutch drum
Brake band blocked Check freedom of movement and
operation of brake band
Saw chain rotates at idle speed Engine idle speed too high Readjust with idle speed screw
LA (counterclockwise)
Clutch springs stretched or fatigued Replace the clutch springs or install
new clutch
Clutch spring hooks broken Replace the clutch springs
Saw chain does not stop
immediately when brake is
activated
Brake spring stretched or broken Fit new brake spring
Brake band stretched or worn Fit new brake band
Clutch drum worn Install new clutch drum