This video is about replacing the oil pump worm gear on a Stihl MS 029 Chainsaw. The worm gear is indirectly connected to the clutch hub using a metal arm attached to the worm gear. When the clutch is engaged and the clutch hub turns it will turn the worm gear and operate the oil pump. The oil pump pumps bar and chain oil from the oil tank to the bar and chain, thus lubricating the bar and chain. If the oil pump is not working correctly than the bar and chain will not be lubricated properly.

The oil pump is located behind the clutch, and removal of the clutch is required to get to the oil pump and worm gear.