happy you talked to Bob K. something to try but don't forget where you started from incase you end up being happier where it was.

i would open up the center carb 2 1/2 turns on both idle screws. then turn in the idle screws one at a time checking as you go while covering the air bleed and checking for a rpm change. if the rpm drops, richen the mixture, if rpm increases, lean the mixture. do thse one at a time and when you are done do it again. after you are happy that there is no change in rpm, the using a vacuum gauge adjust the idle on the center carb. then check it again.

all this is assuming that the timing is setup where it needs to be.