Ryobi trimmer mod. RY30040A?

To keep from having to remove the back to stop the engine from rotating, an old spark plug with 14mm threads (same as stock plug) and about an inch long can be used. Remove the electrode an anode from the bottom of plug to prevent damage to the piston. Remove your original spark plug and screw your new "special tool" into head.
This should contact the piston near the top of stroke .
Just remember to replace the "special tool" with your regular spark plug after you have reassembled the clutch.

Jim Hughes
April 2009

Yes there is an allen screw. I just removed it. It has regular threading, ie. lefty loosey. It is a small standard size not sure of exact size. You need to keep piston from spinning while you loosen it so take back assembly off and insert small screwdriver handle into piston assembly to stop rotation. You'll also need to remove clutch weights which screw right off. Again these are normal threads. Good luck

Mike
April 2008