QB Kingfisher & Osprey

[Paskoya]

I've been having a closer look at the carburetors; an Amal 416-1 from the Osprey, and an Amal 420-4 from the Kingfisher, with 95 and 115 jet sizes respectively. Given that the 420 came from a motor with a fuel pump, can it be gravity fed only, or is a pump necessary?

Are these mixture screws? And if so, why are they only on the 420?

They aren't listed in the 416 exploded view, either. Whats going on?

[Charles uk]

The 420 can be gravity fed provided you don't have a requirement for high fuel flow.

The 1 suffix carbs had both screws not used.
The 4 suffix denotes fitted with the tickover adjuster screw (also requires a stop button), & mixture screw.