Tuning Carb Issues

[nzbobc]

Hi folks,

Just starting having some issues. So, first off, I thought I'd try to find out more about the carb on our car. The engine is a 650cc off of a s126. The carb has "Alquati" and 23-23 on it. Couldn't find much on the 'net. And, it looks pretty similar to Weber 30 DIC.

We recently got the car and it's been running fine. Then, we replaced one ignition wire and put petrol in the tank. But now, it's acting like there's water in the fuel line: It coughs regardless of speed and it won't idle. We've drained the tank, pump, and line, and replaced the filter. There were a couple teaspoons of water.

Usually, I go back to what I just did/changed and will find that's the problem but I don't think it's the wires. I'm thinking this because when the engine is warm, it runs smooth when I hold the butterfly valve slightly ajar.

Maybe I bumped something when I put the new wires on. I've mainly thought that carbs need little work unless they were just serviced, etc.

So, any initial thoughts? Any diagrams for this type of carb? If I have to, I'll take it off to study it to see what screws control what and check the linkages.

Cheers,

 

[Seabeehenry]

Check the choke screw. Could be clogged.

 

[Toshi 975]

Hi Bob,
I think that you have answered your own question there. Water in the petrol ! Water in the tank is a nogo , being heavier than petrol it will lay in the bottom of the tank nearest the pickup , get drawn up & some will lay in the filter and also be in the bottom of the carb float chamber where the main jets are. Coughing and spluttering is very consistent with water in the fuel. You need good clean fuel in the tank and you may be able to blow the water out of the system with a good long blast but if not, and it sounds like you have a Weber (or Holley made under licence) 30 DIC carb, then the two main jets can be removed (10mm socket) lower left of the carb . This will drain the float chamber so be prepared for petrol ! but it will also drain any water. If that works I would recommend something like Redex in the petrol to clean the system.
The 23-23 carbs were the later ones, the exact model will be stamped on the side of the mounting flange either side of the idle mixture screw which you will not be able to see as it will be up close to the rocker box cover. Earlier carbs had a 23-21 venturi ratio . Alquati , I guess, is cast into the side of the inlet manifold. Original Alquati parts are very rare so I wonder if your engine has other upgrades. It is also hard to find out much information about Alquati but off the top of my head I believe that Camilo Alquati headed up an Italian racing team in the 1980's and he was acknowledged for getting the best performance from the 2 cylinder air cooled engines and also the 131 twin cam engines.

 

[nzbobc]

Thanks for the info...

As for the carb type, right you are Toshi: Alquati is the manifold. The carb itself is labeled, "Weber 7F 30DDF 1/253"

I'm not up to speed yet on the different carb models. At some point, I'll have to do a little more research since this carb, coupled with the inlet manifold, make the air intake pipe sit right up against the top of the engine compartment. Whoever had put the 126 engine (or this carburetor) in had to remove the engine cover latch to make it fit. I haven't seen other photos yet on the 'net that look like this setup.

 

[nzbobc]

So, another question...

As I'm doing some research on carburetors to come up to speed, I need help identifying one part.

The carb I have is a Weber 30 DGF. Chris posted a photo of it in this thread:
https://www.fiatforum.com/500-classic/301381-new-again-forum-3.html?p=3059767
(post #34 )

In the photo, on the side of the carb facing the camera is a diaphragm looking thing. It's gold in color, round in shape, and has some linkage coming out the top. From the pdf he posted, the part name is: Boite de dispositif appauvrisseur. Google Translate didn't help. What is this part?

I ask because my carb doesn't have this.. And, does anyone know who has such parts? I've looked at the websites of the usual 500 parts suppliers but none offer this.

Cheers,

 

[Bambino]

Hi nz,

The french word appauvrissement translates as impoverishment (pauvre = poor) and the device to which you refer is part of the accelerator pump.

As far as I understand, accelerator pumps can work two ways. The bulk of the fuel can be injected either as the throttle butterfly opens or once it is fully open. In the first instance, the accelerator pump valve opens early and closes late, in the second it is closed early in the throttle butterfly movement and opens once the butterfly is also fully open.

The two styles of pump are named after the flow of fuel at full butterfly opening.

Thus the first device with no, or poor, flow at full throttle is the 'weak' or 'depletor' or 'appauvrisseur' style of pump whilst the device with full flow at full throttle is the 'rich' or 'enrichment' or 'enrichisseur' style of pump.

The depletor types give a short squirt and shut off thus preserving fuel economy whereas the enrichment type (as in the Weber DCOE and your DGF) give a long and lusty squirt resulting in a good turn of speed but at the price of somewhat poorer economy if used constantly.

The carby pictured in the old post is a DGS.

I've attached a schematic of the two types.

Hope this helps,

Chris

 

[nzbobc]

Oops,

Sorry Chris, I meant to thank you earlier for posting this info. The part in question is actually the choke pull-off:

https://en.wikipedia.org/wiki/File:CarbNomenclature.jpg

For some reason, my carb doesn't have this. But, since the car starts smooth, I'm not too worried about it.


Still having some issues with this carb tho:

The idle mixture adjusting screw faces the rocker cover. I can't get at it with even the shortest of screwdriver bits. I'll have to fabricate something to adjust it.

But worse yet, is the screw is frozen solid! It was moving nice and smoothly until I decided to "clean" the carburetor by soaking in a bath of hot lemon juice. Won't ever do that again! It ate away some of the aluminium and the threads for all the screws and jets are now very rough. Gonna have to see if I can coax this soft brass screw out...

 

[Bambino]

Sorry - I thought you wanted to know what a "boite de dispositif appauvrisseur" was ...

A 'choke pull-off' opens the choke slightly just after the engine starts to minimise the chance of flooding. It's normally operated using the inlet manifold vacuum. Not all cars need them and not all carbies have them.

Hot lemon juice - interesting. I've heard of molasses to get rid of rust and coca-cola to clean radiators, but never lemon juice as a carby cleaner. You learn something new every day.

Chris