The Solex B40 PA4IO-5a Carburetor thread!

That's very valuable input, Chris, and thanks or welcoming me.

The tubing is indeed 1/8", but as far as I can see the port has the same diameter (not 6mm) and there is no apparent way of removing the tube.
There is however an open threaded port right next to it (see picture) which looks like it could be 6mm (haven't measured it yet). It's also difficult to see if those two ports communicate, i.e. if there is an open passage between them.

If there is, does this mean I can cut/blind the old tube and mount a new one in the threaded port using the part number you refer to?

I don't know how much vacuum we are talking about, but is it possible to use a thick-walled flexible hose -such as a fuel hose- instead of messing about with stiff copper tubes, or will the hose collapse?


Einar


P.S. Pedro: It has indeed had a hard life. Some metric violence has also been exerted. Someone removed the 5/16" nuts and used raw force to mout 8mm nuts instead. It hurts to look at it...

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Originally Posted by EISTO

That's very valuable input, Chris, and thanks or welcoming me.

The tubing is indeed 1/8", but as far as I can see the port has the same diameter (not 6mm) and there is no apparent way of removing the tube.
There is however an open threaded port right next to it (see picture) which looks like it could be 6mm (haven't measured it yet). It's also difficult to see if those two ports communicate, i.e. if there is an open passage between the

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Isn't that for the mixture control screw?
.W.

Of course it is, how embarassing :D


I'm getting a bit confused by the figure in my manual. There's something strange here. I decided to remove the tube, and there's no trace of an olive or screwed union (16 & 17 in below figure). The tube seems as if it was just pressed into the carb body. The hole is the same ID as the tube.
My guess is that the screwed union has snapped just like Chris mentioned, and that what remains is so rusted that it just looks like grit.

I guess Plan B is to either try to clean out the remains of the union screw or drill/thread a hole and fit the tube with a larger diameter union.....


Einar

G'day Einar,

Yes the port you refer to is as others have reported is for the volume control screw (idle mixture adjustment.)

Yes the tube nut has broken off and the wall thickness is only 1mm so it is hard to see. A tricky job to remove it with the pipe in and only takes time or usually a hard pull will get the tube out. Usually the broken bit can be unscrewed out.
Use plenty of penetrating oil first by blanking off the hole into the carby throat and filling the broken tube up and leave for awhile to soak. Use a fine tipped screwdriver blade inserted in the centre of the broken tube and try and back out the screw. Maybe fine pointed "broken screw extractor" could be used?. It will come out.!!!!

Yes you could rethread to a larger size however think you will get the broken bit out and find the olive at the bottom of the hole.

Yes the original tube is all steel because of the vacuum however the Zenith carby uses a short length of rubber hose to connect to it. The Solex uses the tube nut and olive method to connect to the carby.

Hope this helps
Chris

Thanks Chris, I appreciate it. I'll try using some WD40 and do as you say, hopefully it will come out. I couldn't find any online store selling the tube assembly (279724), so I'll try to get hold of whatever parts are available -such as the oilve and screw- and pehaps buy some 1/8" tubing and assemble it myself.


Einar

G'day Einar,

Just a further thought: The problem of re tapping the vacuum port to a larger size may cause another problem. It may break into the volume control screw port and cause air to leak into the idle circuit.

If you cannot repair the original vacuum port I use the 13mm boss in the casting below the vacuum port for a vacuum gauge port.

Chris

As an alternative to retapping the hole larger I have had good success with this Loctite Form A Thread Repair KIT Gray 4 8ml | eBay

The best thing is you can form what ever thread type you wish :) The original fittings are being made in unobtaniam now I think.

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Hi,

Chris: Could you explain (perhaps show a picture of) what you mean by "the 13mm boss in the casting below the vacuum port" and how this works?
Scott: Good stuff. I don't think it'll work in this case (see text below) but I'll definitely keep it in mind for future ruined threads.

My cousin (the owner) and I tinkered with the Solex last weekend, but didn't get much further. Strangely, there is absolutely no trace of the broken "screwed union". Only the olive remains.
When I scratched the walls of the hole with a screwdriver, I noticed it was aluminium; not steel. Was the screwed union made of aluminium, and is that what I'm seeing? I could swear what I'm seeing is part of the carburetor body; there is no trace of the screwed union, although the hole is just 4mm across.


Anyway, there is no way to restore the original thread, so we're planning to drill and tap the hole. I though I'd try making a 6mm or 1/4" thread. Hopefully, this will not cause me to break into a nearby channel.
The plan is to insert a barbed hose fitting for hoses with 1/8" inner diameter and use a small length of hose to connect the copper pipe to the carburetor. Same thing on the distributor side.

Therefore: What is the thread size of the connection nipple on the vacuum unit?We're talking Series IIA, not Series II (my mistake). I need to know in order to buy the correct hose fitting. The car is located 2500 km away in northern Norway, so I can't measure it myself...


I really appreciate your help :)




Br,
Einar

G'day Einar,

The 13mm Boss I refer to is in your photo you posted and is 20mm below the centre of the vacuum port. It is the raised round casting and you can drill and tap the required size hole in this and a small 1.5mm hole through the throat wall for the vacuum.

However, if you are going to retap the original vacuum port obtain the fitting first to determine the thread type. It can be BSP, NPT or other and note you are aware of breaking into the volume control screw port.

The thread on the distributor vacuum connection end could be a number of thread types or a tube for rubber hose connection. Unfortunately you are going to have to measure it. It may not be an original distributor as well.
(I don't know what the original thread is. All mine are tube and rubber hose connections.)

Foot Note: The 1.5mm hole thru the throat wall is not in the centre of the M6 hole. It is on the lower edge. This allows the throttle plate to clear the hole and not block it when the engine is idling.

Hope this helps.
Chris