I have a R51/3 engine that I am tearing apart. The engine is the same as the /2 engines. One of the pistons is stuck in the cylinder. The engine does not turn over. I got one of the cylinders off, but the other has the piston completely stuck. I can unbolt the cylinder from the case and turn the crank, but again the piston will not move within the cylinder. I tried soaking it with some penetrating oil for a couple of hours. I also applied heat to the cylinder (got it to the point it was too hot to touch), but absolutely no luck. I tapped the cylinder lightly with a mallet to see if I can get it to break loose, but it did not work. Any suggestions?