The non-serviceable bit relates to a seal, the later type of seal that is bonded to metal ring, which can't be removed without destroying the feather valve assembly, due to the bearing being pressed in, blocking access. The service bulletin is S-E 093, which was added to this thread;
They eventually made the same change to the induction housing too, must have increased profits on service parts, why change two cheap seals, when they could sell a complete new feather valve & induction housing.
David