>>**Remove the Boom/Shaft from the Engine. >>On this trimmer, there is a T20 Torx Screw Inside the Coupling Drive that has to be Removed. You'll need a T-handle driver or a torx key set to get in there. Jam a long flat screwdriver into the underside of the starter assembly to freeze the driveshaft. >> Once the coupling drive is out of the way, you'll need to remove the clutch. It's threaded (standard r/h) on the drive shaft. Use channel locks to remove the clutch assembly.