When you cleaned the carbs did you use follow this?
Rebuilding VB Carbs
The rubber plugs cover the slow jets. They are needed since the slow jets are supposed to get their fuel through the primary main jets. If they are missing the bike will run very rich in the mid range. The slow jets are not removable so cleaning them requires special attention.
There is a 5mm screw in the head just ahead of where the carb insulators attach to the head. Install vacuum adapters where the screws go to sync the carbs. That sounds like a good bet for the source of your problem.