Put a piece of soft rope in the spark-plug hole leaving some out for later removal (after removing the plug) turn up against the piston totally stopping it, use a drift punch on the clutch, there should be several raised casted lugs on the main body for this purpose. Just a sharp rap on the drift should do the trick. This is how most saw shops do it! Clutches and sprockets require maintainance fairly often and I have done this a number of times over the years. Very easy after doing it a few times.........