Hi Maylar, this is how I see it. Tickling floods the idle circuit but also the needle jet and may also put fuel directly into the inlet manifold, giving you a rich mixture for starting. If we don't do this then we would need to create enough vacuum in the inlet manifold to suck the air out of the idle circuit and then draw the fuel up it, mix it with air and inject it into the manifold. All through a hole just 0.016 inches wide. We just can't get enough vacuum with a kick to do that.
When running, the circuit is kept full by the vacuum but when we stop so does the vacuum and fuel drains back down, replaced by air. We are back to where we started.
The time taken to get there varies from bike to bike, altitude, rate of evaporation, fuel volatility, leaking gaskets, sync of carbs etc etc.
The choke extended into the airflow helps a cold engine by increasing the vacuum over the two tiny inlet ports on the engine side of the carb but perhaps more by blocking some air and making the mixture richer until you get to operating temperature. It doesn't really help the bike fire up though. I don't have a choke fitted at all and usually start first time after tickling. Doesn't matter if its hot or cold. I just look after the idle till its warmed up.
The pilot screw controls the idle mixture but is set in conjunction with the air slide that controls RPM, ie vacuum. As you pull away it hands over to needle jet pretty much instantly. It does have a range and is ideally set to make idle and transition optimum.
In my view both the idle and needle jet contribute to starting with success dependent on availability of fuel in the jets. I always start with some throttle.
So in normal circumstances full or half tickling is normal. If you are stalling due to problems in those circuits and then struggling to start then there is some scope to investigate why. Otherwise just get the timing spot on, valve clearance right and then sync and set per the Bushman instructions (Adjusted for slide size) and learn roughly how long you get before you need to put fuel in those circuits by hand...