solex carb from b172k questions

[andrew]

Hi guys,

disassembled my solex a bit and got several question, maybe you could help.

1) secondary ventury plate does not open with primary. Secondary plate moves freely by hand when i pull the lever on its axle, but doesn't react when i rotate primary's axle at all.
what lever is supposed to operate secondary ventury? Am i missing a link between primary and secondary flaps? i see a spring on the primary axle, a stopper boot on primary axle's lever and a choke cam lobe, but i understand they all operate secondary plate to close it.

here is what i have, both plates are closed

primary open

more shots


2) i found someone's made a small hole in primary plate, should i plug it in order to make carb to operate properly?


3) how do you clean float chamber?


any help appreciated.

[mac]

Hi Andrew - a simple problem with a simple answer - your secondary throttle link disengage latch is seized in the active position. (Closing the choke flap operates a spring loaded latch to deactivate the secondary throttle butterfly)

Using photographs of one of my rebuilt carbs I will try to make things clear.



In the above pic,
A = the primary throttle shaft
B = the secondary shaft
B1 = secondary throttle adjustment stop screw
C = choke cam
C1 = choke on throttle progression adjust
D = secondary throttle deactivation sprung latch
D1 = latch spring (note retracted position)
E = the link to the secondary throttle

With the choke in the open position, opening the primary throttle causes the linkage to connect with the sprung latch and operate the connecting link to the secondary throttle



Further opening the primary throttle causes the secondary to follow


With the primary throttle fully open you see the secondary throttle has also fully opened



In this pic the choke flap has been closed and the choke cam has activated the sprung latch - note the spring is now in the extended position (much like the seized latch on your carb)



On opening the primary throttle the linkage bypasses the latch and the secondary throttle cannot open



As for the hole in the primary butterfly I can only assume that it has been done to bypass a non functional idle circuit. The carb is designed to idle with both butterfly closed with the idle mixture entering the primary venturi below the primary throttle plate via the idle circuit passages (which also has the idle shut off solenoid in circuit). Drilling a hole would allow air to be drawn through the closed plate carrying fuel from the main jets thus allowing some sort of idle. If the idle circuit and solenoid are fully functional I can see no reason whatsoever for the hole. (Solder it up)

The float chamber can be cleaned by soaking overnight in either carburettor cleaner or white spirit followed by agitating with a stiff artists bush or wooden "toothpick" - the chamber and all the various passages should be blown out with a high pressure air line.

In truth rebuilding a carburettor is one area in which a degree of expertise and knowledge is needed - if you have further questions please ask.

I hope the above is of some help and wish you the best of luck.

Mac.

[andrew]

brilliant, better that i could imagine.
Mac, thanks again for your insight.
Can't wait for my gaskets to arrive to have another go on rebuilding this carb.

[mac]

Hi again Andrew, just a few comments before you tackle your Solex.

Looking at the pic you posted of the float chamber,



The brass plug labelled X is an accelerator pump pressure bleed off jet. When you open the throttle the accelerator pump injects extra fuel into the venturi to give a richer mixture during the acceleration phase. In the interests of reducing emissions some of this fuel is bled back to the float chamber via this jet - however it can cause hesitation as you transit to full throttle and was deleted in later versions of the carb. You will do no harm by soldering the jet orifice shut.

The pipe and 'O' ring labelled Y forms part of the idle circuit - ensure the 'O' ring is undamaged and if you can blow out the pipe with an airline.

The jets labelled Z are the air correction jets/emulsion tubes - if you remove these (don't mix them up) you will find the main jets below them - you need a long thin driver to get them out. Again blow out with an airline.

I can also see what looks like a crack on the edge of the bore for the accelerator pump jet (next to the bleed off plug) - if this is damage make sure it does not progress down further than the 'O' ring on the body of the pump jet (which has the pipe/s directed into the venturi)

Test the idle shut of solenoid by earthing the carb body and applying +12V to the tag on the solenoid - you should hear a distinct click as the idle jet opens, remove the power and it should click again as the jet shuts (sealing the idle circuit).

Check that the base of the carb body is perfectly flat - any distortion will give you air leaks (and great difficulty in setting the carb). Over tightening the carb fitting bolts will cause more war page - and not cure an air leak). If distortion is present either "dress" the base flat with 320g "wet n dry" or have it milled flat.

Mac.

[variomaticus_dl]

Hi together,

following up Macs posts I have a question about the types of the Solex carb:


left is the carb from my 1,7 340 redline, right the one I have bought.
How do I connect the two nozzles of the right one in my car?
For what are they?
What types of carb are the two?

Thanks and best regards.

Matthias

more photos:
the new:


the carb from my car:

[mac]

Hi there Matthias,

"Your" carb is an early Solex Z10 from (almost certainly) an '86' year model and would not originally have been fitted to a Redline. (The "give away" is the shape of the top of the venturii - the later carbs had an extra casting on the side for a breather passage - early air filter housings will not fit later carbs without modification)

Your "new" carb, whilst it is a Z10 is not from a 340 (there are various versions of vacuum and breather pipes but I do not recognise this configuration). The larger of the two pipes in question is a float chamber vent pipe (you will also see the vent valve arrangement is different. This pipe would vent to atmosphere (under the car) or more likely into an activated carbon filter canister. The other pipe appears to be a "return" to purge the carbon filter.

Such systems work by a canister collecting float chamber vapours which are purged under conditions of high manifold depression but such a system was never fitted to the 340.

Various versions of the Z10 were used by the 400 series, as well as Renault, Peugeot, Lada, and even Mitsubishi.

I would be inclined to lead the "large" pipe to a position under the car and cap off the small pipe.

Good luck - Mac.

PS - why not refurbish your carb?

[variomaticus_dl]

Great Mac!
Thanks for the big overview.
Yes I want to repair the old one. But I am confused about the other, because it is sold as an ex-340er carb.

About the pipes: the bigger pipe seems to be never in use. Is is rough and dirty. The small one is blank and obviously connected to a tube.

Bye Matthias

[mac]

Matthias,
further digging suggest your "new" carb could well be from a 440/460 with a B18KP engine.
Whilst not being fitted with a carbon canister they did employ a rather more complex float chamber venting arrangement than the 340 B172K - see 400 series bulletin below.





If you think I can help further just give a shout.

Regards - Mac.

[variomaticus_dl]

Hi Mac,

this means that the small vent pipe simply goes to the engine mounting
The big one only stays open?
What is the other tube?

Thank you very much!!

Regards Matthias

[mac]

Sorry Matthias I'm not sure which "third" pipe you refer to.

Apart from the vent pipes discussed there should be a main CV Breather on the black insulating block, the fuel inlet pipe, and a vacuum source for the Renix.

If you could post a clearer pic of the pipe you mean I will try to advise.

Mac.

[variomaticus_dl]

Mac, yes this is clear.
I mean the other tube in the picture, goin to the engine mout, too.

[Chris_C]

The B18KP is jetted differently to the B172K, as it used a different cam. Renix used was different also.

[mac]

Good morning Matthias,

I agree with Chris, the "new"carb would not be a direct replacement for the correct version.
It may well have been fitted to a 340 at some time (it would work after a fashion) but it wouldn't be right.

As to the vent arrangement - I'm not familiar with the exact functioning but the "usual" way these things work is for a fairly large vent pipe to be open when the engine is off (to prevent a rich mixture collecting in the venturi and causing a difficult hot start) and a much smaller vent bleed when the engine is running to allow maintaining ambient pressure in the float chamber. The large vent would be controlled through a solenoid valve.

It looks as if this is the way it works on the 400

Does anyone know the truth of it???

Regards - Mac.

[mac]

Been digging around a bit more.

On the 400 with the KP engine there is an "early" and a "late" venting system - the "early" does not have the additional vent from the 'T' piece to the engine mount. In both systems the vent solenoid is energised when the engine is started - the float chamber is vented for 3mins (via a timer relay) if the under bonnet temperature is above 70c (thermal sensor on the manifold). Looks like the permanently "open" pipe from the 'T' was added to increase venting.







My digging has raised a further question - on the 400 Z10 the vent pipe exits the float chamber at 90deg, on yours Matthias it exits at about 30deg leading me the think maybe this is not from a 400 after all - most likely a Renault. (Or there is a variation in carb versions on the 400)

Any 400 experts like to comment??

Mac.

[andrew]

does your breather pipe looks like this from down under?

i'm by no means an expert but on russian solex carbs there is a breather hose which is usually suggested to be blocked.