AJS & Matchless Owners Club

East Suffolk Section

Technical Tip (21) Spark plug threads in cylinder head

A simple tool for the maintenance and repair of cylinder head plug threads can be quickly made out of an old spark plug. Carefully file four “V” grooves up the length of the threaded part with the Vees angled slightly to the left to give cutting edges to the grooves.
Heat up and quench to harden the new “plug tap” and it can happily live in your tool box until it’s needed.