1978 Choke pull off adjustment on a Weber 32 ADFA 14

[lvacordian]

The Weber ADFA manual mentions a special tool (fiat tool 4900) that is used to make the choke pull off, minimum and maximum opening adjustments. Can I use a vacuum pump on the port connected to the diaphragm to test the choke pull off openings, and if so how much vacuum should be applied? Secondly does the pull off diaphragm mechanism include a bleed valve that would prevent me from testing with a vacuum pump, and what is the typical PSI rating for manifold vacuum on a 124?

[majicwrench]

Yes just use a vacuum pump. Just suck it up, engine vacuum,10-20 what is the unit of measure?? Inches of merc?? Something.
Not sure on old weber if they had a diaphram with a bleed or not. Many domestics had a bleed that made it tougher to use a vacuum pump to test diaphram. I would just suck on it and see. If it is just a simple vacuum unit and it wont hold vacuum, it is bad.
PSI is not how they measure vacuum, so I don't understand question.
Keith

[manoa matt]

The adjustments described on page No. 10 are usually sufficient. I haven't seen a rebuild kit in a long time that includes that diaphragm, so the existing one is usually hard and doesn't move much.

You can perform the adjustments on page No. 11 with the proper diameter drill bits to check the choke plate min and max opening. Just find a fine thread metric screw that will thread into the choke housing body and it will take the place of tool No. 1 as shown on page No. 11.

[lvacordian]

That is a great idea. How long should the screw be? I was thinking that would be significant to the relationship between the amount of manifold vacuum versus the the tension on the chokes thermal spring. I know the manual says that the two have to balance each other out in order to achieve the correct minimal and maximum choke pull off openings. I was thinking that the tool might be calibrated to a specific length in order to be representative of the intake manifold vacuum at startup. The manifold vacuum will pull the diaphragm back at a specific distance, where a screw that is too long, or too short might push it in too far, or not enough. Either might result in an inaccurate measurement of the openings. I'm also worried about damaging the diaphragm with a screw that is too long. Does anyone have the tool for sale, or know of the specs on the tool? Then again perhaps I'm overthinking this one.

[manoa matt]

I've rebuilt around (15) 32 ADFA carbs in the last 7 years or so. Since the diaphragm is NLA/cost prohibitive if found, I've only done the adjustments on page No. 10 and all carbs ran well. I only tinkered around with using the screw to replace the tool on my own carb and did not notice a difference in performance or operation. It has to be a pretty long screw for the diameter and thread pitch so finding the appropriate screw is a hassle in itself. I doubt anyone has that tool.

"Then again perhaps I'm overthinking this one."

Yep.

[lvacordian]

Thanks Matt. California emissions testing tends to make one paranoid. I appreciate your good advice.