Carburetor Idle Filler Tube – How far to screw it in?

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Carburetor Idle Filler Tube – How far to screw it in?

Postby Virginia Joe » Fri Apr 26, 2013 7:58 pm


I acquired an IH Carburetor that had no idle tube in the carburetor. I ran 4-48 bottoming tap down the hole to clean it up and I did get plenty of good threads showing inside. What was strange is that the tap never really bottomed out, it instead went into a lower cavity and bottomed out on the casting below. Then, when I put my new idle tube in, it went so deep I’m afraid it will interfere with the idle adjusting needle.
Did I run the tap too deep and if so, how do I know how far to screw the idle tube in?

What I was thinking of doing is installing the idle needle first, than install the idle tube until it hits the idle needle? Then put a dab of thread lock on it because there is a little wobble in the tube when screwed to that depth. What do you think?

Any and all advice is appreciated. :mrgreen:

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Re: Carburetor Idle Filler Tube – How far to screw it in?

Postby ScottyD'sdad » Fri Apr 26, 2013 8:09 pm

The idle tube has a short amount of threads on it. It should stop, before going in too far. Ed
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Re: Carburetor Idle Filler Tube – How far to screw it in?

Postby Bus Driver » Fri Apr 26, 2013 8:41 pm

Possibly the threads were tapped too deep in the effort to clean them. Remove the idle mixture screw and blow out all passages before doing anything else to the carburetor. Metal chips could be a big problem. The idle tube screwed in finger tight should be quite good-- no tools should be used.
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