The trick with the perry's is not to let it act as a pump to put any inlet pressure on the needle, let the carb design do the drawing of the fuel. The pump should be looked at as just a device to get the fuel there and thats where its job stops and the vacuum of the carb picks up and takes it from there. These little carbs dont work as fuel injectors very well.

When setting one up, use a spare tank to let the engine run on, and let the standard line empty into a cup and adjust it so it just brings fuel up to the end of the line. Even a steady dribble comming out can be too much flow and act strange with needle settings. Remember the carb will still have a draw effect on its own.