Frank.
My Centaur sucks fuel from the bottom tank I don't have a NR valve in the fuel line, but I found that you must have the light spring acting on the valve in the carb, my engine wouldn't run without the spring, having said that I have a Wyvern engine which does run without a spring on the carb valve.
Mike
Edited By MichaelR on 16/04/2017 11:31:48