18.6.0.4 Carburettors:
a) Any round-slide carburettor of a type 
available pr e-1975 may be used 
except the Pre-1960 class where a Mk1 
Amal Concentric or period carburettor 
may be used.
b) Flat-slide carburettors are prohibited on 
all machines except EVO and Pre 85,
c) No reed-valves permitted on machines 
up to and including Pre-1970 class
John ,the rules don't actually state which type. I can understand where you are coming from but as Taka says, it needs clarification 
