That is an old down draft flo-jet carburetor. The part your referring to is call a nozzle. Yes it must be removed during the disassembly and re-assembly.
Also note that these nozzles are prone the leaking as they use a metal to taper seal. If this is a problem then you need a new nozzle as the following fix will destroy the old one. Using old nozzle file off the threading, Now using the old nozzle using a fine valve lapping compound on the taper polish the seat in the carburetor. Once polished and cleaned, install the new nozzle and it should be leak free.
Plus the main mixture screw can be a problem leaking if an after market assembly is use as the their threading is too loose to match what Briggs used.
Hopefully around has the IPL for this one as the Briggs Power Portal here doesn't show one although they show 141331-5006-49 as valid number.
