su balance confusion

[clindayag1]

I have just purchased a Haynes Automotive Repair Manual for my 240z. This is my first time tuning carbs and have followed everything step by step and now have run into some confusion. On sec 16, #19 it says:

"set the fast idle screw so that there is a clearance at its tip of between .039 and .079 (1 and 2 mm) when the balance screw is lightly depressed with the finger."

i cannot lightly depress the balance screw because its screwed down to keep my carbs balanced. the only way to lightly depress it and make that 2mm clearance is to completely slacken the balance screw so the screw is not touching the thing that its suppose to push down on. but that would unbalance the 2 carbs.

[John Coffey]

You're assuming the clearnace should be on the balance screw. The clearance is between the fast idle screw and the linkage. Lightly push on the balance screw while making sure there is a clearance between the fast idle screw and the linkage.

[clindayag1]

oh i get it now. im such a noob:stupid:. now, i dont see the point of this procedure. so the clearance is now 2mm when i lightly press on the balance scew. when i let go, the fast idle screw is now touching the metal thing that it pushes down on. couldn't i have just screwed the fast idle screw down till it just touches that metal part and not have to measure the clearance?

oh also, when i lightly press down on the balance screw,thus slightly revving the engine, the rpms go from 650 to like 2000 is that normal?

[Friar-Tuck]

CDY1,

I also was quite taken aback at first by the several different ways I found online to tune these critters.

I am no expert by any means, however ZTherapy.com has two videos that clear up everything.

I got the "SU's only" tape for about seventeen dollars .

The earlier Zcar tape has a short carb tuning segment and valve adjustment etc.

If you can swing it or will be keeping the SU's I highly recommend the tape. It is a bit Dated(2000) and the sound quality was pretty rough but you'll save yourself the seventeen bucks or so in frustration and see exactly how to service and tune those thangs.

Tuck\o/