I adjusted each carb so that each has the same power setting at high and low throttle. This is important because each carb independently operates 2 cylinders and, if not in synch, excessive vibration will occur. Procedure: Advance throttle levers to full, then back off so that you can insert a snug feeler gage into one, then adjust ferrule on the other throttle cable such that the same feeler gage is snug. Next pull throttle all the way back to idle. Ensure that at the idle stop, no gap exists between carbs. If so, adjust idle screw so that they are the same with no gap.
I've got them set and will go with these settings at start up. If excessive idle, I will back off each idle screw same amount, e.g. 1/4 turn. If vibration still occurs, there is a way to synch carbs pneumatically by hooking up pressure gage and making sure differential pressures in intake manifolds are the same.
