I bought a used had been sitting a while 2001 600S from a friend. Started, ran on choke, would not take throttle with choke off and warm. Pulled the carbs (hardest part is the "puller" cable), did a thorough cleaning, shimmed the needles with one shim each, removed the pilot plugs and set the screws at 2.5 turns. The bike runs GREAT. No lean sag, no surge, screams up to redline.
Caution - I used the radio shack shims and miked them to make sure they were same (they were). I did notice that they do NOT fit into the little circular well in the slide very good. I had to file them
(reduce OD) to make them fit (loose fit) into the well in the slide. Otherwise the shim wouldn't sit flush and it would hold the needle up (and make plastic retainer clip difficult to install).
I'm posting this so others will know the bike can be made to run well with the stock mains and pilots, shimmed needles, screws at 2.5 turns.