the drilling it out part will work fine.
normally the Mikuni 22/26 have a #15 or a #17.5 fitted standard to them
most of the one's i've worked on when you blip rev them, there is a slight hesitation
a #20 seems to fix this problem in most, but a couple with a little work (bigger pipe, matched manifold) have needed a #22.5
might pay to check your float level too,
do you have any 3mm o/d clear pvc hose, cut a length about 6" long.
slip it onto the drain tube at the bottom of the fuel bowl, and hold the other end of the hose up at the same height as the top of the carby.
now undo the drain screw at the bottom of the fuel bowl, and check what level the fuel comes up to.
measure down from the fuel bowl mounting face to the fuel sitting in the tubing.
it should be down about 25mm from the top of the bowl
when you cleaned the Pilot jet out, did you poke some wire through the holes ?
if it gums up a little, the hole size can halve, and not let enough fuel through, but still look open
same thing with the hole through to the carby bore, at the bottom of the threaded hole that the Pilot jet screws into, poke something through it, then give it a good blow out with compressed air.
even blow the air into the threaded Pilot jet hole, and check you can feel it coming out the big hole on the r/h side of the airfilter side of the carby
and last thing, the Mixture Screw port can get dirt/gum in it, and not let much fuel through too
it always pays to remove that screw/spring when cleaning them out, and again, compressed air is your friend.