Thanks for the reply. My carbs, like most of the parts on my bike, are from a different model, the B1 and C1 models which are fitted with a pilot air screw on the side of the carb, marked 53 on this diagram

According to the Haynes they should be between 1 and a quarter and one and a half turns out. Hence my curiosity as to the amount of air being permitted in with the ridiculous amount of turns the previous owner had done.