used 

 -   amal pre monobloc     type 276 76 carb  mixing  chamber  top / choke plunger ass

with often missing locating clip

may need a longer spring fitting ?

typical sunbeam s7  s8 models 

alloy /di-cast type top  - brass plunger 

must be 70 + years old

bsa  

triumph panther ariel norton ajs matchless royal enfield dot sunbeam