Quick question about 11009-1240

I recently bought a set of BS34s from a KZ1000 csr. Anyway they are missing the rubber plug 11009-1240 on one carb . On my other BS34s the metal plug is glued or soldered in place. So my question is do I really need the rubber ring? Does it hold the metal piece in place. Could I epoxy resin the plug in place and forget the rubber ring alltogether?

I believe the plug must be sealed with an o-ring or something as the passage needs to be sealed properly for proper fuel uptake.