I have one with a metal mesh insert. The insert I have is called a spark suppressor or flame arrestor. These air cleaners were used mostly on marine applications. If the kind you speak of has a device attached to the underside of the lid, that may be a sound deadener with a matt/hair filler. Some air cleaners had a vibration noise. As mentioned you don't want anything/material there where bits could possibly fall into carb/intake/engine. Get rid of it. Owners (knuckleheads) have been known to add a "spacer" to fit a wrong size element.


Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn