Does anyone know what the function of this diaphragm/valve is? There is one per carb, on the side and I would need to seperate the carbs to check # 2, 3, 4. If----I knew what they did I could determine if they were working properly without having to go to all the additional time and expense to visually inspect them. I have the carbs off to check float height, jets, needles, screws etc,. while seeking to correct a mid throttle lean condition. I have the factory Homda manual and they don't mention it. (1979 Honda 750 LTD). I want to get the machine on the road. Thanks. Jake