The clutch spring holds the weighted shoes near the shaft of the STIHL 180 chainsaw. At a certain rpm, the weights overcome its force and press against the drum, transmitting torque to the sprocket.
Replace it if it is stretched, broken, or there is a noticeable difference between the springs: the chain starts to rotate at idle, or the clutch engages late. Usually all the springs are replaced at once.
After replacement, check the unit at idle and under load: there should be no leaks, play or unusual noises.
