LAWN MOWER SPARK PLUG J19LM REPLACES PLUG NO J8, J8J, CJ8 and J8C. REPLACES PLUG NO J8, J8J, CJ8 and J8C. LAWN MOWER SPARK PLUG J19LM. Standard Spark Plug J19LM. Standard spark plugs use a copper core, for improved conduction, and traditional electrode designs.