Weber 40IDA3C & 40IDA3c1: idle jet carrier washer and idle mixture o-ring questions

[ghalperin]

My carbs are numbered 1051 & 1091.

I'm cleaning up my carbs and during disassembly I noticed no washers on the Idle jet carriers, also no O-rings and cups on the idle mixture screws.



I found a photo online that shows a washer.



Is the idle jet supposed to bottom out in the carb body?

I installed washers and it doesn't appear to be correct.




The idle mix screws didn't have O-rings or cups.

Should I get the cups and install the O-rings?

Do I need to replace the springs if I install them? Are there specific springs?

I looked online, but didn't see the cups offered anywhere.

Lastly, should I install gaskets on both sides of the air filter base?

Thanks for any help.

[classic]

Glenn,

Can you post a photo of your idle mixture screws? From memory the design changed, some use the cup and O ring and some don't.

Re the air filter base, if your fitting stock, it should be a large gasket over the body, cleaner base, individual gasket and then the trumpet.

[edmayo]

I don't know where that idle jet picture came from, but a copper washer was never used, later models did use an o-ring, but not the carbs in your picture. It may have been the IDT's that used the cup and o-ring on the idle mixture adjusters, but again, not your model. Paul Abbott is the expert, hopefully he will chime in.

[ghalperin]

I found the idle jet picture from Ekchuah. http://home.comcast.net/~ekchuah/Weber.html

I have no idea who this is, but the weber parts photos and descriptions are nice, although the idle jet carrier is mounted with a washer.




Below is a photo of my idle mixture screw with spring and idle jet with carrier.
.

[Ernie W]

Weber IDS diagram may help. #43 is an O ring, and #65 and #66 only show a jet and the holder, no washers.

[1QuickS]

You have the early bodies and idle jet carriers, no o-rings or washers. Later bodies had a larger port and the jet carriers had a reduced diameter just under the head to allow an o-ring. If you use "late, o-ring" idle jet carriers in an "early" body then the idle jet will not seat.

Early bodies did not use cup washers but there is no reason why you can't do the same. Also, you can use an o-ring under the head of an early idle jet carrier and it will deform to create a seal without affecting secure seating of the jet.

Mixture screws and springs for the IDA, IDS, IDT, and IDAP bodies interchange, the IDTP bodies used a stepped-tip mixture screw which I believe was to prevent the standard tip with continuous taper from being seated too tightly and then twisting off during removal, the stepped tip has a larger diameter that will not go into the bleed hole so it can't seize the tip. The IDTP mixture screws don't adjust as nicely as the normal tips do. ALl bodies use the same spring for mixture screws and idle speed stop screws.

[Jm993rs]

I'm suscribed to this !!

[Merv]

Can I update this one? I have the 40IDAP3C Webers. There are no O-rings fitted at this stage on the Idle Jet carriers. Also while checking the jet settings with a pin gauge set, I was able to confirm that they are 0.60mm, and stamped as such.

Two questions then,

1.0 should these early carbs have O-rings? I would think so. (I eventually found a nice thread on this)

2.0 what is the correct idle jet size for these (US 1968N)?

I have seen 0.50 and 0.55 and 0.60mm?

[Merv]

No suggestions on the stock idle jet size for a 1968 US 911N on Webers? 0.50, 0.55 or 0.60mm?

[edmayo]

Trusting to memory they were likely 55, try them and see how it goes. Easy enough to change and experiment with.