It sounds like you've hit it, but just to be complete, here's Clymer's 11-step program towards more harmonious carb operation:
Before starting, check your timing, valve clearance, and idle speed.
1) Put the bike on the centerstand, start it up, and let it reach normal operating temp.
2) Shut it back off. Pull the rubber caps from the intake manifolds.
3) Connect the gauges.
4) Start the engine. The normal reading should be 18-24 cmHg. The difference between any 2 cylinders should be less than 2 cmHg. If the difference is greater, proceed as follows.
5) Shut off the engine.
6) Remove the fuel tank. Unless you like fire hazards, don't rig up a temporary supply, just run with what's in the bowls.
7) Remove the top covers from the carbs and loosen the locknuts.
8) Start the engine and let it run at idle.
9) Fiddle with the screws until all carbs are within 2 cmHg of each other. Backing out the screw decreases vacuum, turning it in increases vacuum.
10) If, after completing this procedure, any carburetor reads less than 14 cmHg, this indicates trouble within the carburetor. Take it apart and clean it.
11) Remove the test gauges, reinstall the four manifold vacuum caps, and reinstall the gas tank.
