Cleanliness is the difference between a rough idle and a smooth-running N14. Learn the professional procedure for using the M20139 copper brush. The Danger of Improper Bore Cleaning Many technicians reach for a standard steel wire brush to clean injector bores, but this is a critical mistake. Steel is harder than the cast iron or aluminum of the cylinder head; it can score the sealing shoulder, creating a path for fuel or air leaks that a new copper washer can't fill. The M20139 uses copper bristles specifically because they are softer than the head material. The 5-Step Cummins Bore Prep Debris Check: Use a shop vacuum to pull out any loose flakes before inserting the brush. Tool Setup: Secure the M20139 in a variable-speed drill or a comfortable hand driver. Low-RPM Scrub: If using a drill, keep it on the lowest setting. Insert the brush and apply light downward pressure to the seat area. Visual Inspection: Use a bright light to ensure the bottom "ring" of the bore is shiny and free of carbon rings. Final Flush: Use a lint-free swab and a light solvent to remove any remaining copper dust or residue. Why Shop Owners Trust Apex TECH TIP: Replacing N14 injectors is an expensive job. Don't let a $30 tool be the reason a $3,000 set of injectors fails to seal. Keep an M20139 in every tech's bay to standardize your cleaning process. Professional Grade Tools for Professional Results. Get Your M20139 Today