Ok a question about Carbies. Main jets are used to limit fuel flow (top end). The needle is to regulate flow. A number of questions arise: a) Is the needle jet the jet through which the needle slides? If so why would you vary the size, when you normally vary the shape and setting of the needle? b) Is the pilot jet just at idle or at low speed also? At idle, the mixture is effected by the mixture screw, so what is the correlation? Does the mixture screw set overall mixture? c) What is the air jet? Is this for the choke?