My advise is if you manualise your choke, It's critical that when the choke is on, the butterflies can flutter. Otherwise the engine wont be able to get any air, and it'll run crap. People always try to manualise the auto chokes on valiants. I've lost count of the number Of vals I've seen with choke cables added to. they were alway hard to start. The water chokes on the cortina webers have a bimetalic spring. (Much like the vals had) they enable the butterfly to flap. (Especially while cranking) I even utilised the spring on my old weber to keep this feature, when I manualised my choke.