DS Weber adjustment
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Thread: DS Weber adjustment

  1. #1
    Fellow Frogger! badabec's Avatar
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    Default DS Weber adjustment

    Hello, 1974 DSuper5 with Weber DMA2 carb. I have fitted oversize spindles plus rebuild kit. Now I am trying set the idle speed.
    The manual, operation D-142-0 says on no account fiddle with the throttle stop screws but it doesn't give the correct setting.
    I'm sure that over the last 40 odd years someone will have fiddled with them.
    Any idea what they should be set at?

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  2. #2
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    Hi Peter

    All is not lost! Have you seen the literature here?CitroŽn DS/ID and XM Web-Site

    If you go to the DS 'Technical data' section, there is a subsection all about carbs. This includes some original Weber material for various carbs. Some in French, others in german. these might just have the figures/ tolerances you are after. More useful though, is a general weber carb set-up instruction. at the top of the carb page. See the 'general adjustments' section of that document. It says that the screws should not be fiddled with - but then goes on to explain what to do if they do need adjusting.

    Regards
    Paul

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    Marvellous, thanks. I'll use a fag paper to check the gap before I start to adjust.

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    Hmmmm... just had a read. They're pretty basic instructions. I'm sure someone on here can do better.

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    Quote Originally Posted by badabec View Post
    Marvellous, thanks. I'll use a fag paper to check the gap before I start to adjust.
    With all 2 barrel Weber on the later cars the idle is set with the secondary barrel - that clearance mentioned is just the starting point. Do ensure, however that the throttle plate on the primary is set properly. IOW the bottom edge of that throttle plate should just, as in just, be covering up the first progression hole in the throttle body. Use a low powered magnifying glass to double check. Once set, lock the adjustment screw with its lock nut and then double check again to insure it has not moved .

    And before setting the idle do insure that the engine advance is correct as well as float level in the carb as well as spark plug condition and condition of the fiber insulating tubes and wires. Again all of that info in is 814 and supplements.

    Steve

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    Quote Originally Posted by Citroenfan View Post
    ...the bottom edge of that throttle plate should just, as in just, be covering up the first progression hole in the throttle body. Steve
    I have the same carb and struggling to get the tune just right. In reading through this post i'm about to head into adjusting the "locked" spindle screws and would look at the direction above to help guide...although i have a basic/dumb question. When you say "first progression hole" are you talking about the first hole that is closest to the intake manifold or the first hole from the top of the throttle body? I suppose i'm interpreting "first" as the one furthest away from my eye as i'm looking down into the throttle body from the top of the carb. I'm going to pull the carb for this operation as i can't even see a progression hole all the way down the throttle body from the top....i'm guessing it's better set from underneath?
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    Default Carb adjustment/set up

    I have a couple of articles I refer to. The attached is my favourite.
    Attached Files Attached Files
    forumnoreason and JohnW like this.
    M.BERRY
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    This is just a case of RTFM. (F='factory' here!) Remove the carby and follow the instructions and pictures, which are clear enough, on how to initially set up the butterflies and linkage before you fiddle with mixture and idle. It's possible to (mal)adjust the dual throat Webers so the second throat doesn't open properly.

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    Quote Originally Posted by David S View Post
    This is just a case of RTFM. (F='factory' here!) Remove the carby and follow the instructions and pictures, which are clear enough, on how to initially set up the butterflies and linkage before you fiddle with mixture and idle. It's possible to (mal)adjust the dual throat Webers so the second throat doesn't open properly.
    Thank you David! Very much appreciated.
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    In manual 814-1, Op 142-00 notes the primary butterfly stop is to be adjusted to allow a '5/100' feeler gauge (0.05mm) to slip between the butterfly and bore. The secondary butterfly would be just closed. However, Op 142-0 has a clearer picture showing the butterfly stops to be initially adjusted.

    Also be wary of a warped base that might leak air. The bottom corners tend to creep under tension over time.

    If it hasn't been apart in a long time, this might be a good chance to service it, clean out debris and check the float and valve.

    Consider making the change to a screwed in fuel inlet barb to replace the press fit tube that works loose, with a bad result.
    Last edited by David S; 3rd October 2017 at 02:31 PM.

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    Okay. I give up.......

    I'm setting the mechanical adjustments on the Weber carburettor of my DS after a strip and rebuild. WHY has the throttle stop screw gap got to be 3.8mm when the choke (strangler) flap is fully engaged (closed)? (Operation D.142-00 in 814/1 refers). What does it achieve and how do you get that measurement?

    In it's idling position, the throttle stop screw on the primary bore is set to just cover the first progression hole (or 5/100th gap) and locked at that setting. Closing the choke flap pulls on the vertical rod which operates (rotates) the primary shaft to expose the first and second (and third) progression holes.

    The instruction is that if the gap at the throttle stop screw is NOT 3.8mm, then to bend the tab that the throttle stop screw is screwed against. Why? What does that achieve? Bending the tab does not affect how much the primary shaft is rotated by the rod?

    If the intention is for the rod to rotate the primary butterfly (from it's idling position) by a number of degrees as measured by the throttle stop screw gap (3.8mm) then the only way I can see to do that, is to limit the movement of the rod at the top end? To do that but still have the strangler flap close fully, means bending the little tab on the strangler shaft by the little spring.....BUT, to do that you would need to bend it by a silly amount. Not feasible.

    I'm clearly missing something here. Happy to be put right.......
    1968 DS21bvh Pallas in Gris Palladium

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    Budge, I won't weigh in with responses to your specific queries, but in the past I've had great difficulty setting up the Weber carb on my '74DS23 automatic. Citroenfan Steve (16th June - nearly a year ago - in this thread) really knows his stuff in this area and will hopefully respond to your specific queries.

    In parting, I should add that I found that my carby had a slightly warped base (refer David S, 3 October) and resolving that by fitting a new spacer and gaskets using a petrol-resistant Three Bond sealant (to 'fill' the warp) made an enormous difference. I also recall that setting the primary throttle position to just cover the first progression hole was very fiddly.

    Apologies for not being more helpful.

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    No. That's very helpful in wider terms. I'm sure the principle (for idle) is to 'just' cover that first progression hole, but that's open to interpretation. Also the 814.1 (alternative?) requirement for a 0.05mm gap is tricky because you are measuring on the curve of the bore, not the flat.
    1968 DS21bvh Pallas in Gris Palladium

    Restoration blog: https://ds-restoration.blogspot.co.uk

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    Budge, I hope Steve doesn't mind me passing on his private communication here, but this is what he advised me in regard to the primary throttle setting a few years ago:

    "First off - the purpose of setting the primary throttle plate at a nominal clearance is to position the plate so that its bottom edge (base side of the carb) has just covered the first of the progression holes drilled in the primary venturi. The progression holes are a series of little holes that are supplied by the low speed jet. The purpose of setting the throttle plate at this position is so that 1) Excess air and or fuel is not introduced into the engine at idle and 2) that you don't have a 'dead spot' coming off idle on very light use of the accelerator pedal. It really is a quite touchy adjustment.

    If you have the engine idling normally at this point I would suggest you try the following (should prevent you from having to remove the carb and setting that throttle plate visually with the aid of a magnifier). Get engine to operating temperature. Slacken the primary throttle plate adjustment screw so that it is just touching the stop. Reset idle speed using only the idle mixture screw and secondary throttle plate. Once that is done slowly open up the primary throttle plate to the point where the engine speed has increase around 50 to 75 rpm. Then readjust the speed using only the secondary throttle plate. At this point turn the idle mixture screw CW a bit at a time until the rpm just starts to drop. Then move it back to its position just before the rpm decreased.

    This should get you very close to the proper clearance for the primary throttle plate.

    Setting the throttle plate clearance with a feeler gauge is a bit tricky as one has to press fairly hard on the plate to get an accurate measurement."

    I agree, trying to use a feeler gauge - or even a narrow sliver of shim stock - to set the clearance is not easy!

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    Thanks for your reply Citquery: it confirms my understanding of the throttle stop screw and progression point. With the screw fully open my throttle plate only just covers that first progression hole anyway. I suspect it's that way be design, but if they then fit an adjuster, it implies that the 'sweet spot' is less easy to set.

    I'm still not clear on all that 3.8mm business when the choke is operated, but have resolved to let that lie for the moment as i really don't understand the setting and what it's trying to achieve.

    Budge
    1968 DS21bvh Pallas in Gris Palladium

    Restoration blog: https://ds-restoration.blogspot.co.uk

  16. #16
    bob
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    G'day,

    Quote Originally Posted by Citquery View Post
    .......Setting the throttle plate clearance with a feeler gauge is a bit tricky as one has to press fairly hard on the plate to get an accurate measurement."[/INDENT]

    I agree, trying to use a feeler gauge - or even a narrow sliver of shim stock - to set the clearance is not easy!
    consider, maybe, using a set of twist drills to measure this curved clearance....

    cheers,
    Bob

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