Very unusual to see a holed piston, it is normaly due to detonation caused by ignition timing out, poor fuel, or people useing piston stops to remove clutches, not too sure what the dealer will say, have you taked this thing apart to see this hole? is it a nice round hole, or does it look like it is eroded around the edges of the hole? nice round holes are normally due to the use of a piston stop, eroded holes are due to detonation.
Husqvarna man, April 2010