I tried for the first time last night what I thought was a great tip I picked up off a forum here. To use a rope laced into the sparkplug hole for a piston stop. I found a barely run Chinese JF (MTD-McCulloch) 50cc chainsaw. The saw displayed very little use - that's because the magneto was loose and apparently they threw it away rather than bothering to take the cover off to see what made the ugly screeching noise. Saw ran excellent. I began to dismantle for conversion to airplane engine - decided to try the rope in the sparkplug hole - got the reverse thread nut off OK but it was tight - tried the flywheel side and it was very tight. Had about 8" long 3/8 ratchet wrench on the nut - braced the base with my elbow/arm - pushed down on rachet handle with left hand and rapped with small claw hammer. Busted the piston into 4 pieces. I don't have an impact wrench and have used the wrapping hammer technique successfully before many times with no hazard when I have had the flywheel clamped or braced. I am not a gorilla - force was maybe ill advised but not excessive - any body else have this happen or was I just unlucky. I heated the nut to loosen it - wished I would have the first time. Engine looks great otherwise - anybody got a piston for sale? One interesting thing - the screws and bolts on the engine proper were all "excessively" tight - like impact wrench tightened - screws and bolts on the housing were all loose or barely tightened and I don't think anyone had loosened to inspect - they were never tight.