Whenever I build a carb, I let it soak disassembled in carb dip for about a week. I would check your valves like the others suggest.
Pull the plugs and read them. I would also double check the carb boots to see if any are loose and you have a small vac leak.
If you are bound and determined, take the carb back apart, here is my method:
(Note that I've never done a vol carb, but it has worked well on holleys, and my GS550s carbs I've done)
Disassemble, remove jets and let it soak. Then blow through all the passages with spray carb cleaner. Pay special attention to the little holes near where the throttle plate closes. Make sure you find where to spray to make carb cleaner come out of those holes. They are your idle and transition jets and most likely to get clogged.
Take a brass wire brush and pull one of the wires out and stab it into the butt end of a match stick. Use it to clean the jets. Scrub them good n clean.
Put the float needle in, hook a piece of hose to the fuel line and give a gentile blow. If it leaks, then you need to repair or replace the seat.
Install the float. Set the height. Set the height again. Check the height. Then set the height again.
Finish re-assembling and button up the carb. Spend alot of time checking for vacuum leaks. Double check all boots.
I think there is only one carb on a VOL so there should be no need to sync them. (This is a major pita on a quad carb setup).
Here is a link:
How to Clean a Motorcycle Carburetor, the RIGHT way. » Evan Fell Motorcycle Works
-Hope some of this helps