How to replace a clutch:
1. Remove the clutch cover, bar, and chain from the saw
2. Remove the top cover on the saw to expose the spark plug
3. Remove the spark plug
4. Get your self a piece of clean nylon cord about 12” long and stuff about 4” inches of it or so in to the cylinder through the spark plug hole. (make sure none of the rope works it’s way out through your exhaust port, otherwise you’ll have little bits of cord to clean out of your cylinder).
5. Find the appropriate sized socket or specialty clutch removal tool to fit on the center of your clutch mechanism. (Some specialty tools can be improvised but that’s another story).
6. Unscrew the clutch by turning to the right because clutches are left hand thread, that is most clutches, some old American made chainsaws are regular thread. (The cord that is inside the cylinder should keep the piston from moving and allow you to apply plenty of torque to get the clutch off. If the motor manages to turn over while you’re wrenching on it just stuff more cord down inside the cylinder).
7. Assembly is the reverse of removal.

If you have an old Jonsereds, some old McCullochs, some old Craftsmans and old saws with West Bend engines your flywheel is keyed onto the crankshaft. You can use the above procedure to remove the outer nut, but you will need to remove the clutch mechanism like you would remove a flywheel.

If you have a newer Stihl with an inboard clutch you need to remove the c-clip and clutch drum before using the above procedure to remove the clutch.