How to Change a Spark Plug on a Craftsman 6.75 Lawnmower

Pull the spark plug wire off the existing spark plug. The spark plug is on the front of the engine.

Turn the spark plug counterclockwise with a 5/8 inch spark plug socket and a socket wrench. A spark plug socket has foam gasket material inside to help prevent cracking the porcelain insulator. A standard 6-point 5/8 inch socket is an alternative if you do not have a spark plug socket. Use care when using a standard socket to avoid breaking or cracking the plug insulator.

Set the gap on a new Champion RN4C spark plug to .030 with a gap tool. The most common gap tool is a round disc with a graduating outside perimeter or individual wires of various thicknesses. Insert the .030 part of the gap tool between the hook ground electrode and the center electrode. Adjust the hook ground electrode with the notch on the gap tool as necessary until you have a .030 gap.

Thread the new spark plug into the spark plug hole in the engine until it is hand tight. Turn the plug another ½ turn with the socket and socket wrench. Push the spark plug wire over the top of the spark plug until it snaps into place.