Working on the Wingnut Wings Roland C.II kit. I'm building the scheme with the Lewis gun and small radiator header. Does anyone know the function of the tube assembly attached to the fill pipe?

I'm specifically interested in parts A and B in the photo. "A" appears to be some kind of clamp which secures a small diameter tube that terminates in the small funnel shaped object "B". Why is it attached to face forward and upstream of the pilot?