Mixture Screw Spring

[79Temecula]

Hi all,

First post on here! I bought a '79 Spider 2000 (CS2) here in California and have spent the past few months learning all the fun things that previous owners thought were good ideas.

I recently decided to tackle the carb since it was flooding into the air cleaner. Turns out it's a 34 ADF underneath (unfortunately still using the dual plane intake and 4-1 exhaust along with much of the emissions equipment still in use--though no cat surprisingly). I'm completely rebuilding the carb with important things like gaskets (only had the top gasket before!) and going back to factory settings as a baseline.

However, I found that the mixture screw spring is missing. According to the 32 ADF diagram there should be and I'm having trouble finding a replacement. My understanding is the spring keeps the screw in place and prevents it from moving, correct? Seems like a smart idea to have it then. Anyone have thoughts on where to find one? I assume a 32 ADF spring would be the same.

Thanks in advance for any help!

[18Fiatsandcounting]

Yes, these little springs can be hard to find. Try Pierce Manifolds in Hollister CA or FiatPlus in Santa Cruz.

In a pinch, you might be able to hold the mixture screw tight with a small locknut. Very early models had such a setup, which was actually kind of a pain because you had to set the mixture with the screw, and then tighten the locknut without turning the screw. The spring setup is much nicer.

-Bryan

[79Temecula]

Thanks, Bryan! Pierce didn't have it but FiatPlus did (I think).

[bobplyler]

still using the dual plane intake and 4-1 exhaust along with much of the emissions equipment still in use--though no cat surprisingly

The 79 came with 4-2-1 exhaust.

[79Temecula]

still using the dual plane intake and 4-1 exhaust along with much of the emissions equipment still in use--though no cat surprisingly

The 79 came with 4-2-1 exhaust.

It's a California 79, so 4-1 exhaust.

[79Temecula]

Alright, I can't seem to figure out whether my 34 ADF mixture screw even came with a spring. The 32 ADFA mixture screw w/ spring isn't deep enough to seat properly. However, I noticed that the original mixture screw rubber gasket holds the screw in place on my 34 ADF. Anyone else see this before? I've scoured the internet and can't find another like it.

Original screw seated

https://flic.kr/p/2oFLYqn

Original screw compared to 32 ADFA scew

https://flic.kr/p/2oFNwTA

[Nut124]

Just looked at your pictures now. Your original screw that has the o-ring and is in a bore does not use a spring. Only the screws that are "external" use a spring. The o-ring keeps you screw from turning.

[davidbruce]

What nut said. Hard to tell from the picture but it looks like the original screw was seated too aggressively at some point. If you can catch a fingernail on it and/or are having trouble getting a good mixture i would keep looking for a replacement. Probably not an issue but something to be aware of.

[79Temecula]

Thanks, guys! I had figured maybe the o-ring acted as both a seal and holder, but since I've often heard that the 32ADFA and 34ADF are similar I wanted to make sure I had the right parts.