you can find some tiny tapered reamers at some machine tool joints that will not leave swirl marks like a drill bit (which can affect the fuel flow thru a jet)...with these and a micrometer you can accurately enlarge the jets a little at a time, and know where you're at (but you cant go smaller) if you go too far you can find some old Pinto or other car that used those carbs and get some more junkyard jets and start over. and on jets that aint marked--you can stick the reamer down the hole and then measure the diameter of that part of the reamer...mine are a five sided shape so it aint a perfect (not high point to high point) measure but I bet you can get within a thousandth anyway-its pretty close.
some folks say they have replugged the oversized jet with solder, redrilled it and then resized the jet with the reamer (if the jets are really hard to find).
AAARRRGGG, you said LEANER--I misread-well thats my two cents anyway! some of it is still true--It would be nice to have a pair of "back-up" jets before you experimented too much.
