Hi DenverJayhawk
If you saw no O-ring on the LSNV then you have found the problem. It is not a plain screw. It has flat screw head, then some machine threads, then a goove for the O-ring, then a long small diameter end at the needel end that actually enters the tube that the fuel comes out of inside the carburator throat. You can probably find the manual by Googling for it.