used 

 -   amal monobloc     type 375   carb  mixing  chamber  top / choke plunger ass

but has the often missing  locating / locking clip 

ideal - does away with long cable . lever  and plunger 

alloy /di cast type top  - brass plunger  rod

must be 60 + years old

bsa  

triumph panther ariel norton ajs matchless royal enfield dot sunbeam