Yamaha XS650 Seized Piston Removal
The left piston was seized up in this engine. It took several days of soaking in PB blaster to get it loose. Getting the alternator off enabled the engine to rotate the cylinders up with piston still seized in the bore. See the top of the bore? That's a solid ring of rust that had to be broken loose before piston would slide down bore.
With the cylinders raised up it made it possible to place a wooden block between the bottom of the cylinders and the engine cases. Heat was applied to the piston, then a wooden hammer handle was placed on the seized piston and a five pound hammer was used to tap on it to break the piston loose. It was then possible to push the piston down in the bore.
At the bottom of the bore the piston again stops cold. Wooden block to left with blue tape keeps cylinders raised above cases. More soaking of piston top is needed to get through rings so they can compress so piston will slide all the way out. So far the bores look to be in good shape with no scoring of walls.