Genuine Stihl spring 11256472400 (also sold as 1125 647 2400) - the tip of the worm drive sits in the slot on the clutch drive and when the saw is operating, the crank turning - this drives the oil pump in the saw.
Fits:
- 029, 039 series
- MS290, MS310
- MS340
- 034, 036, 036QS
- MS360, MS360C
- MS390, MS391