If the starter clutch is a square (ish) shaft, the whole assembly unscrews. You will either need a special socket that fits over the clutch, or you can knock it round using a drift on the lugs. Remove the screen for access, then RE-INSTALL the small screws that hold the screen on before attacking it with the drift. If you dont, the clutch will fall apart (not the end of the world, but a real pain).
Let me know if you still have problems.
phil_saunders@bigfoot.com
Phil Saunders, August 2008