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[vern hodgson]

So what are the threads for the idle jet?? Tom Endy seems to say in his article in his article 1/8”x72 pipe thread whereas another article model A dot org claims 5x75 metric. So which?

[Werner]

Good morning Vern, maybe the sketch will help you? I measured a new idle-ventury now. Given in mm because I do not know the funny inch measures in fractions.

[vern hodgson]

Originally Posted by Werner

Good morning Vern, maybe the sketch will help you? I measured a new idle-ventury now. Given in mm because I do not know the funny inch measures in fractions.

Danke,but I am looking for the tap size to re chase the threads in the casting.

[Werner]

O. k., that is a metric 5 mm standard threadt.

[Benson]

All the idle jets in the carbs that I have worked on are 5MM- .75 ... the same threads as the other jets and early GAV seats if the casting has one.

Idle Air Screw is same same.

Idle jets do have a tapered "gasket surface" and as such do not use a gasket like the other jets.


I see where confusion is happening: see post #1

The brass GAV housing is a 1/8th 27 tapered pipe thread. and is 3 times larger that jet threads.

I have heard some say that 10-34 is very close to the 5MM .75.

But when I found castings that were threaded 10-34 the 5MM .75 jets "squeaked" when they were threaded into casting ... Both original and repro jets.

Someday I will have to find a 10-34 tap and try it out!

I have a 5MM .80 tap that is easier to find but does not thread well with the 5MM .75 jets.

[katy]

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Originally Posted by vern hodgson

So what are the threads for the idle jet?? Tom Endy seems to say in his article in his article 1/8”x72 pipe thread whereas another article model A dot org claims 5x75 metric. So which?

1/8" NPT is 27 tpi, not 72

[vern hodgson]

Originally Posted by Benson

All the idle jets in the carbs that I have worked on are 5MM- .75 ... the same threads as the other jets and early GAV seats if the casting has one.

Idle Air Screw is same same.

Idle jets do have a tapered "gasket surface" but do not use a gasket like the other jets.


I see where confusion is happening: see post #1

The brass GAV housing is a 1/8th 27 tapered pipe thread. and is 3 times larger that jet threads.

I have heard some say that 10-34 is very close to the 5MM .75.

But when I found castings that were threaded 10-34 the 5MM .75 jets "squeaked" when they were threaded into casting ... Both original and repro jets.

Someday I will have to find a 10-34 tap and try it out!

I have a 5MM .80 tap that is easier to find but does not thread well with the 5MM .75 jets.

The part that is confusing is Tom Endy s article on page seven which states referring to the 5mm .75 ( DO NOT run the tap through the threads for the idle jet, as these are a tapered pipe thread.). But he does not give the size, this can possibly be assumed that the size is a 1/8-27 pipe. But other articles and comments refer to it as 5mm .75. And looking into the original of two top castings on my work table, one appears to have ape red this and the other does not and that one the 5mm.75 jet balks at going in. My thought was someone screwed it up in the past, so I want to chase the threads, but do not know which tap to use! That is the dilemma.

[vern hodgson]

Correction to read “appears to have tapered thread”