Plug 'm! The only right way to cover up case bore openings. Foreign material that gets into the bottom end can cause major damage, using a rag or shop towel can inadvertently introduce these contaminates. This magnetic case bore plug set fits the spigot perfectly, holds the rods and is sold in a 4-pack set for front & rear cylinder. - Range: 4.20" to 4.575" crankcase bore. / Fitment: 18-24 107", 114", 117", 121" M8 models