the poulan 32cc trimmer and blower engines are about the same as a ryobi, are you saying the piston is stuck in the cylinder after you got it loose? it sounds like you just have a ring stuck in a port, take the muffler off and see if the ring is stuck in the port, if it is you should be able to push the ring into the piston and get it apart, I believe the transfer ports are just slots so it shouldn't be able to get stuck in there.

the poulan saw engines come apart like Av8tor mentioned