attached are pics of two different carbs. both pulled from an f3. im cleaing both these carbs and planing on reinstalling them but before i continue ive been wondering what makes those black shutters go up n down? see as one is two open and two close as the other one is all four closed. is this a problem? or how can i close these, to conclude, wtf. why is one different then the other. thank you for reading.

 

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There could be a problem because they should close on their own. There is a spring under the black cap which pushes down on the sliding cartridge that. When the the carbs are in use, there is a vacuum that is created by a rubber diaphragm that is attached to the cartridge. This vacuum lifts the cartridge and pulls the needle up.

 

Yes there is definitely a problem. What I can't tell from the photo is whether the slides are missing, or if they have gone so far up into the top of the carbs you can't see them. I do see the main jet needle, so I'm assuming that the slides are there, but that they are moving freely up and down and have slid all the way up because the carbs are upside down. Hopefully you're just missing the spring that is on top of them that holds them down, which would be an inexpensive repair.

The slides movement is controlled by the vacuum that's developed in the intake manifold. There is a small hole in the bottom of the slide that allows the vaccuum that is generated in the intake to extend up inside the upper portion of the carbs where there is a diaphram that separates that chamber from upper to lower. As the vaccum develops, atmospheric pressure is able to overcome the spring pressure, and raise the slide. As the slide raises, it effectively changes the size of the venturi and maintaining a constant flow rate through the body of the carburetor. This is why these carbs are called CV or Constant Velocity carburetors.

You'll definitely have to fix this if you want to use them.