Rich A Puyallup , WA March 21, 2015 Appliance: KitchenAid Built-In Microwave KBMS1454RSS0 Kitchenaid Microwave Kbms1454rss0: Microwave was shooting a small flame out of plastic cover. How to replace Waveguide Cover. The inlet cover had a hole burned into it causing an exit for this flame. My research found that food splatter on this cover or a magnatron near the end of its life may cause this. I replaced the cover and all is fine. Quick and easy fix. 6 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: Less than 15 minutes