Small Engines (Lawn Mowers, etc.): Frozen Cylinder, piston rings, prone region

Question
Was given a 4HP Briggs push mower that does not appear to have many hrs, but was left in the elements. Crank froze & I removed spark plug and a steady stream of water came out. Removed head & cylinder was full of water. Appears that pistons corroded to wall, but dont see any pitting or anything. What would be best method to try to free piston up. Everything else looks good except carb had breather left off too


Answer
Toast!!!
Don't waste your time.
I live in a flood prone region and have seen many flooded engines. Unless you bust the piston out, bore and hone cylinder, and replace piston, rings, and probably carb it will never work.
Check out a Small Engine trade magazine (available at most libraries) for adds on wholesale engines. Probably available for less than the cost of OEM parts and machine shop costs.
Good Luck.