Smallest nearest the bellmouth. Jim Best once related to me the way to set the float height…. With the bike off the stand, on level ground and upright, using a small mirror to see inside the bellmouth, gradually swing the float chamber forwards, if a R/H float chamber, backwards if a L/H float chamber, until you just see a blob of petrol appear on the end of the smallest jet. Dry it off with a tissue and see if another blob of petrol appears. Then move the float chamber fractionally back, so that the petrol level is JUST below the top of the jet, so it can be sucked out by the venturi effect by the incoming air, and tighten the bottom banjo bolt to lock the float chamber in position.