Disclaimer: I have never worked on 1200 carbs!
With that said, whenever I clean a set of 1100 carbs and get ready to bench sync, I loosen the idle screw all the way first and then loosen the remaining carb butterflys until they are fully closed. With the butterfly fully closed, you can see a very small port just above the end of the butterfly in the wall of the intake. I adjust the #3 carb first by turning the idle screw until the butterfly just opens enough to cover the hole. (#3 is the fixed carb on an 1100. I think it is #4 on a 1200.)
Once #3 is set, I adjust #1 to the same position (just covering the hole) followed by #2 and then #4. (The opening will be just about .003 of an inch with a feeler gauge.) At this point, I always test the carbs for leaks before I return them to the bike.
With this method, every 1100 carb I have rebuilt (4 total now) starts instantly and idles very well with minimal synching required afterward.
