not quite with you here alf.
The pilot jet should be screwed right into its hole on the side of the carb. Then the adjuster screw, which allows more or less air in, should be put in and adjusted - no petrol will come out as you do this. Something around 1 and a quarter-ish turns out from fully-in should be about right, give or take, on the screw. The wee spring should hold the screw where you set it, no worries.
The jet holder should also be screwed in fully on the bottom of the carb, with the jets themselves screwed fully home top and bottom (needle jet and main jet respectively), and the cover nut screwed on after. No variables involved apart from the jets themselves and you can't change those jets with the engine running.
I find the best way to get the pilot air and throttle stop about right - I'm no purist - is to start the thing with the throttle stop screwed in a bit to avoid stalling; warm it up, then adjust the pilot air screw, starting from maybe one full turn backed off from fully screwed in, until the thing runs evenly and smoothly - and probably quite fast; then slow down the engine on the throttle stop to get the tickover speed you want alonmg with good clen pick-up when you open the throttle. You'll find unscrewing the pilot air screw will increase revs up to a point, then the thing will die of weakness. Screwing it in too far will make it start to choke and the revs will die and it will be very rich at those rpm. Main thing is to have the right pilot needle and main jets for whatever it is, the right needle and the right slide cut-away. Plus a float needle and seat that seal when the float shuts the fuel off. Shouldn't take more than a few minutes to have it running like a clock if the bits you've got are correct and not too knackered. I also find it's a good idea - if you have a carb top for a choke/air slide but no air slide in there, to bung the hole in the carb's top up with something - a blank screw, some goop, whatever. Because a hole up top allows the rapid ingress of a lot of air, which will mess the setting up a lot. If there is an air slide, be sure the thing lifts fully so that when the throttle slide is fully open there is no part of the air slide obstructing the flow into the cylinders. Apologies if you've done all that and this is grannies and eggs.
