1974 Carb - Idle Speed Screw ? (pix)

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:bounce:

Howdy folks,

4/74 FJ40 Stock engine/carb

Which screw is the IDLE SPEED ADJ screw. And which is the FAST IDLE adj ?

Both seem to adj the throttle...

Red arrow (A) = ?
Green arrow (B) = ?



Thanks much,

:)
carb0006.jpg
carb0002_1.jpg
 
Rather than just answer A or B, here's how you can figure it out. This works on almost any carb.

Move the choke linkage so that the choke plate is completely open (vertical).
Now operate the throttle linkage and watch what is going on.
You'll see that one of the screws will be up against a step in the linkage when the throttle is closed. This is the idle speed screw. What it does is limit how far the throttle closes when you take your foot off the gas. When you turn that screw in, it's like stepping on the gas a little bit.

Now pull on the choke linkage so that the choke plate closes. Now you will see that a different screw moves in and takes over limiting how far the throttle closes. That is the fast idle speed screw. That step in the linkage won't go all the way to the idle speed screw because the fast idle screw has stepped in to take over.

Once you understand how it works, you'll always remember it and never need to ask.
 
;p I see where you get your handle!
 
Neither A or B is the idle speed adjuster.

It is the one in the cast iron base that you can't see in the pictures.
 
Neither A or B is the idle speed adjuster.

It is the one in the cast iron base that you can't see in the pictures.

That's not the idle A/F mix adj screw :confused:
 
Oh, never mind - I see it on mine... :eek: Haven't touched the carb since I've owned it.

To the OP - it's below and inside "arrow A"

Thanks Pin !

Also, what do "A" and "B" adjust, then? :D FSM is very vague.
 
Actually mine is different as I have a Calif EGR spec....

Man, I never would have found this adj screw if I had not seen this thread... Almost impossible to see.
carbscrew0001.jpg
 
A is the throttle positioner speed.
B - I'm not sure, but from the location it may be for adjusting the mechanical secondary opening.
 

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