Lightly clean the piston with some Scotchbrite and soap and water. Sand the bore in a circular motion opposite to the way the piston moves. Use any solvent, such as mineral spirits, kerosene, diesel fuel, (stinky), even some WD-40 would be better than nothing. Some oven cleaner will help with the carbon in the head, but don't let it soak too long.

AV8TOR