remove the cover over the bar and chain. find out if the chain spur is inbound of the clutch and drum or outside of it. if inbound then the clutch will have to be removed first which requires a piston stop screwed into the spark plug thread. this keeps the piston and crank still while the clutch is unscrewed. it is often very tight and hard to undo and is a LEFT hand thread. Once the clutch is off, the drum and spur is removed and fitting is the reverse. If the spur is outbound of the clutch, often an E-clip holds it on and is easily removed. I have used string down the spark plug hole instead of a piston stop but there is a risk of jamming string in exhaust ports or worse! Piston stops might be obtainable from garden machinery dealers and are simple to make if you have a lathe and the means to cut the right thread.
dustydes, June 2008
