Your questions: 1...the idle tube. Do you mean the low speed jet? It is brass, about 1.25" long, thin and screws in on top of the float bowl. If it is just buggered up at the screw slot, that may not have much impact on it. Couldn't say for certain without seeing it. 2...the little discharge orifice in the venturi should be left alone. This isn't replaceable, but some people seem to want to try to remove it. Maybe after a few beers. Please look at image 3 below for what it should look like. Hopefully whoever was "working" on the carburetor stopped before it was damaged. 3...the check ball weight in the middle section of the carb. On top of the float bowl, there is a pump check valve. Generally this is brass, about 1/2 inch long, square or triangular shaped with a point machined at the bottom (where it seals into a cone inside the carburetor body)--see first image below. Is this what you're talking about? It will need to be carefully freed up. Maybe with a needle, small dental pick or something like that. You may need to soak it also...possibly some sort of penetrating oil. There is a check ball down in the diaphragm retaining piece, but usually this isn't removed/serviced. 4. Yes, there are 2 springs on the upper shaft and 1 spring below that. Please see image 2 below.
As for the metering rod, here is what goes on there: first, please understand there is a mechanical rod action and when you're operating the carburetor at partial throttle, the diaphragm is pulled downward (by vacuum). At this time, the metering rod is more or less simply controlled by your accelerator rod because the movement of it (up/down) is dependent on the pump lifter link. What I just said assumes vacuum to the bottom of the diaphragm is stronger than lower spring on your rod. Now there is also a vacuum rod action and when the spring on the lower part of the rod is stronger than the vacuum under the diaphragm, then the metering rod will move upward (opening up the jet to allow more fuel to the engine). Simple as it may seem, this is the power circuit of the YF. When the vacuum drops (as would normally happen when your throttle is opened up...engine under load), the carburetor will provide more fuel to your engine. When vacuum stabilizes, the metering rod returns to normal operation. If you study the rod, you'll see it has either 2 or 3 steps machined into it. This allows the main jet to either be more or less restricted and please remember in the YF, fast (unrestricted jet) does not mean down...it means up. Slow (restricted jet) happens when the rod is down. There is a diagram in image 4 below. The rod is adjusted this way: close throttle valve and press down on the accelerator pump shaft all the way. The metering rod should bottom out (contact the bottom of the float bowl) at the same time. The metering rod arm should touch bottom at the same time the metering rod arm touches the pump lift link (between the springs). If the metering rod doesn't hit bottom at the same time as the accelerator rod or if it hits bottom first, then you can adjust by carefully bending the metering rod arm up/down.
Hope this helps. Jon (carbking) posted some good info on the Carter YF just a few weeks ago...
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
