Hi all I have been a member here for a while but been quiet as drifting from the 2cv scene a while ago, as posted recently I have just got myself a 72 dyane 6. I previously had a 72 dyane 4. The only thing i seem to have is an annoying backfire and also accompanied by a massive flat spot from the rested throttle to the instant open, ie after every year change upon opening the throttle its flat, sometimes backfires through the carb then comes to life. Things done .. valve clearances, new points and condensor and timing set with a strobe, timing marks were already on the flywheel, can't remember points gap (as Haynes manual) exhaust gap .25mm I let's .2 mm could it be timing or points or both or insulator block cracked at the bottom of the carb , is it I am expecting to much of it and it's a case of "they all do that"

Many thanks in advance

No, they don't all do that Sir.
Chances are you have an air leak, and it could well be the carb insulating spacer. Also check the throttle butterfly spindle, as when worn they will leak air through.

PS: points gap is .016" (0.4mm).

Thanks Derek I'll try these out..

Does it idle ok?

Have you checked if the nuts securing the carb to the manifold are all tightened down? It's certainly not unknown for them to loosen over time.

TC, it sounds very much as though the accelerator pump is either 'lazy' or not working at all.
Provided that someone hasn't dismantled that mechanism and lost its internal spring, I've found that it's fairly easy to get them functioning again using the following technique.

Remove the rubber intake hose between the air filter and the carburettor so that you can look down into the throat and see the small brass tube which acts as the accelerator pump 'injector'
Next, spray WD40 or similar into the slot where the operating lever sits, then start the engine and hold it at 'about' 2,000 rpm.
(This isn't critical, it's just so that when the pump starts working, you'll be able to detect its effect on engine speed and it also prevents too much neat fuel building up in the manifold.)
Work the accelerator pump lever by hand, with the engine still running at that speed and it shouldn't take too long before the pump 'wakes up' and a jet of fuel can be seen emerging from the injector nozzle with each stroke of the lever.
That will cause the engine to stumble for a few seconds, then pick up again.

Btw, which model of the 26/35 carburettor is on your engine, a 21-24 or an 18-26?
Both types require re-jetting to run best with unleaded fuel and the Ami/Dyane style 'forced induction'...

hi roger yes she idles ok all best slower when cold as in just about.. then when warmer more satisfactory

Hi Ken, ill check the carry size and let you know, and also look at the injector to see if its working as per your thread, what size main should i be running? i take it this is removable without taking the carb off? thanks for all your help!

sorry i meant carb size!!

The size of the replacement jet depends on which version of the 26/35 you've got.
For a 1972 Dyane, it would originally have been a 21-24, but as with everything else on these vehicles, it may have been replaced...

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