If you get the piston out in one piece,inspect the cylinder.If it has score lines,into the aluminum,it's junk.Make sure that none of the chrome,is flaking.If this in tact,proceed to the next step.What I am about to tell you,is a hap haxard fix,and not first class,but rather shade tree mechanic.Remove the rings,and mark them as to position,and placement in the grooves.Do not sand the piston.Take a file,and remove the high spots on the score marks,of the piston.Clean the cylider with a scotch brite pad.Use this,also ,very lightly on the piston.If you can get it cleaned up,check the fit in the cylinder,without the rings installed.Make sure it doesn't hang up anywhere in it's travel.Make sure the ring grooves are clean,and reinstall the rings,and the rest of the engine.If you can get it to run again,run it rich on fuel about 24 to 1 on oil.The reason you don't sand a piston,is a little known fact about the dull coating on the piston.In the auto industry,this is called"tin plating",but is actually an anodizing process,done to the piston,for several reasons.Reason 1,is the fact that the plating,retains oil.Number 2,it resists galvanic action,a phenomina that occurs when different metals are in contact with one another.I suspect,that the rings were stuck,from the previous posts.You might get lucky.