I know some guys have ran NiCaSil cylinders with the plating MISSING,,about a nickel sized patch. The thing is though,it was BELOW the exhaust port. Now,if you are like me, you just couldn't handle knowing your engine was being ran in that kinda shape...even IF it has been done before,with success. That stuff is TOUGH. That being said,i'd probably call whoever you bought the cyl from and see what they recommend just to be safe.