In servicing my bike at the 55000Km mark, my mechanic discovered the piston actually had a bad surface cut and the piston block also had scratches - signs of engine seizure probably induced by previous owner. Based on recommendation I purchased a new piston (down some $300).
Never mind the price, new break-in distance for brand new piston + rings - 3000Km!
Maybe I should pay house visits to distant friends more often now....