Originally Posted by Anonawesome
Just an idea. The petcock on the stock tank is vacuum operated with a hose running to the carb. Whereas the acerbis petcocks are not. Not sure if the pumper carb has this since I just ordered one, but you could have an open vacuum line on the side of the carb, which would need to be capped.
This is true for the CV carb, but not for the pumper carb. The petcock for the pumper carb is the simple on/off/reserve affair with no vacuum connections whatsoever.