BENCH SYNC: A little bit hard to describe, but here goes....
1. Set the 4 thumb turn idle screws as described in manual. Wind them in until the sideways “T” mark on the shaft is just disappearing into the carb body and lined up with the raised rib on the carb body (viewed from above). All the slides should now be bottomed evenly.
2. Make sure all 4 top adjuster nuts are screwed fully down into the carb tops. You will notice all 4 outer cables can be pulled in and out of the adjuster 1/4 to 3/8” without moving the slides. Unscrew the adjuster enough to eliminate that slack, without lifting the slides.
3. At this point, I mount the other end of the cable to an old throttle tube, and mount it to an old set of handle bars, on the bench, with a scrap switch housing.
4. Open the throttle, with the twist grip, about 1/3 of the way and lock the throttle tube to the bars with vice grips.
5. Go back to the carbs and use the top adjusters to get all 4 slides the same height off the bottom of the carb through bore. I find a drill bit (the blunt end) that just scrapes under the lowest hanging slide. Adjust the other three to match and lock all 4 jam nuts.
This should be good to get you started. I then sync the carbs at idle, using my Motion Pro sticks, with the thumb turns. Finally, use the cable adjuster at the throttle tube end to take any new slack, out of the main cable. Make sense?.