The Official 356Talk Forum

I have searched and searched, but I cannot find the answer to the following question:

How do Solexes with dependent and independent idle differ? Are they different designs or can a 'dependent' be made into an 'independent'?

I have seen sketches of 'independent' carbs, but none of the 'dependent'.

Regards,

Hi Roland,
as far as I remember, normally indipendent Solex were used at 912 and dependent at 356.
And - again as far as I remember - dependent can be made into indipendent and vice versa.
Best
Richard

Split shaft have more hole for fuel between idle and full throttle, more progressive.

that's what i've put on the roadster, split shaft model

fred ©

That's right Fred, 5 progression holes vs 3.
The issue with split shaft is the play due to the adjustment system which makes synchronisation of both butterflies hard to impossible and makes global adjustment tricky. (one butterfly being on the second progression hole while the other one beeing on the third for example...moreover you have left and right carb to synchronize as well!)
On mine, I have taken best of both worlds by replacing the adjustment pieces by a self machined aluminium piece. It gives really better result ! It is now acting like a solid shaft despite being a split shaft base with smoother progression
Here's a gallery showing before and after and work in progress at the end of the gallery.
http://img156.imageshack.us/slideshow/w ... f1564h.jpg

Hi all,

Thanks for your replies, but I was not discussing split vs. solid shafts.

As far as I have understood it 'dependent idle' refers to a coupling between main and idle circuitry making the carb close to impossible to adjust. The carb was later improved by making the two circuitries independent

I am trying to understand this difference, fx. through sketches, but I have not found any.

Regards,

independent - when the fuel entering the idle circuit comes directly from the float bowl

dependent - when all fuel goes through the main jet first and then branches off to idle circuit and main circuit

the problem is that the solex gone worn out with age, so impossible to adjust !!

fred ©

As far as I have understood it 'dependent idle' refers to a coupling between main and idle circuitry making the carb close to impossible to adjust. The carb was later improved by making the two circuitries independent

I have not heard this theory anywhere before. Supposedly, the only difference is that the dependent type requires a larger main jet to feed the additional fuel to the idle circuit. The fuel requirements for the idle circuit are small and should be well serviced with either type. Remember also that the Solexes have a high speed enrichment circuit and that the accelerator pump circuit bleeds fuel at high speed. Of course, making the carbs work at wide open throttle is the easy part.

Hi C J,

Exactly the answer I was looking for. The 'theory' is simply my description of the working modes of the two carbs. I now understand better.

If I understand you correctly, it is not a big issue since both versions are equally tunable

Thanks.

Hi Roland,

Yes we are NOT talking about the difference between the Solid and Split shaft Versions of the Solex P11-4 ! The Split shaft had the Superior Progression Circuits but the nightmare throttle shafts, The best Solex is the Split With the Extra Progression Holes Converted to Solid Shafts. A few of our Registry Artisans are experts at this Conversion.
The First Earlier Type of Solex P11-4 was the Dependant Idling Version, Identified by the Smaller but Taller Brass Float Chamber Vent Tube. To be Avoided!
If the Main Jet is changed for a Different Size it affects the Idle Circuit, Very difficult to Tune and to Quote our good friend Duane Spencer (Hope you are doing Well Duane)
"These have to be the most Frustrating Solexes that were ever made as they will try the patience of the easiest going Person to try to set them up properly"

Cheers

Jay