I read online somewhere where the piston comes apart inside seizing it in place, but I even tried starting fluid with no luck.
Well, starting fluid goes in the air intake, and changes the gas/air mixture.
Sea foam goes in the gas, and is supposed to dissolve gunked up gas. It's been a while, but I think you're supposed to put it in the tank, cycle some into the fuel system by pulling the start chain (slow. don't start, just work new fuel into the lines) then let it sit for so long.