RE: K&B .65 Sportster (yup, more from me)
Does your spray bar have a small slit where the hole is in the spray bar? I looked at the disc/spray bar assy. on my 65 so I know there is a very small slit cut where the spray bar hole is. The only way I know to measure the holes near the disc and the hole in the spray bar is to check them with drill bits. Which ever one(s) fits the holes is the size of the holes.
I'm guessing your problem is the spray bar either not slit correctly or not slit at all. If the slit not there or screwed up, this would affect the low end adjustment. The slit helps the fuel draw at low speed/idle. The rotation of the disc changes the location of the slit in relation to the air draw thru the carb.