Thanks for the pictures Gary . Your second picture shows the slot which the mechanical choke arm slots into locking it in place. Eurocab have said removal of this and or piston requires their cover plate which stops air getting in not unlike the CB kit which is blocked. I agree your link of the reconditioned carburettor does not show the mechanical choke fitted to the outside of the carb, buthowever on this link here https://www.dellorto.co.uk/shop/dell...reconditioned/
one of eurocarb slides on same link number 4 does not show the piston with the slot in it but a solid brass piece which is not unlike CB Performance version:
Here is a zoomed version of same picture
It also looks like the starter jet and starter emulsion tube has been removed?
Great information Gary.
This is a picture of the bottom of the piston showing the shafts