Back in the day we used sized "drills" in the old brass harley tooters...these went by numbers, and I assume but do not know that the numeric designation corresponded to number drills as a machinist would use, ie decimal diameter in inch. It's very easy to screw up a jet, but since the old Linkarts pretty much flushed and there was only one...it didn't matter. I'd save the old jets after cleaning with a "hot" organic solvent and a light reaming - very soft touch, doanascratch the hole...Reynolds number an all... There is, in float bowl situation, some potential for galvanic corrosion...possibly dezincification... if so jets snap off easy,,,,throw away.