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Juddery acceleration on half throttle
http://www.international2cvfriends.com/forum/viewtopic.php?f=7&t=5679		 Page 1 of 1
Author:  Ianredspecial [ July 14th, 2015, 11:14 pm ]
Post subject:  Juddery acceleration on half throttle
It's been like this for a long time now, and the trouble is I can't remember if it was ever any different. If that makes any sense.

Anyhoo it runs like an absolute champ and has always had good power. It accelerates well and idles well, the only thing is if you are only using part throttle it's very juddery.

Resetting the mixture helped a lot but it still does it a bit. My garage did the mixture for me on their analyser since it was mot time anyway.

Is there anything else I can do? Or is it completely normal and just cos it's weeny? Lol. I've had it for 17 years and I just don't remember.
Author:  ken [ July 15th, 2015, 12:18 am ]
Post subject:  Re: Juddery acceleration on half throttle
As long as it's fitted with the 18-26 version of the 26/35 Solex carburettor, change the 102.5 primary petrol jet for a 107.5 and that hesitation should disappear.
Unless the insulating block between the carburettor is cracked, or the 'choke pull-off device' has failed, or there's an air leak at one of the inlet manifold joints or the float level is incorrect.

Things have got quite bad when even the 'garagistes' don't understand that fiddling around with the idle mixture won't have any significant effect once the throttle is opened past the point where the progression drillings for the carburettor's idling system have been exposed and the engine is under load.

Once the throttle is opened past that point, it's all down to the size of the primary petrol jet, the size of the air corrector jet, the drillings in the emulsion tube and the level of the fuel in the float bowl.
Lack of knowledge, perhaps? :roll:
Author:  Ianredspecial [ July 15th, 2015, 8:51 am ]
Post subject:  Re: Juddery acceleration on half throttle
Thank you Ken. I was thinking jets but I don't know why.

The carburettor block is OK, as are the inlet manifold and the choke seems to disengage well. I'll get in touch with Roy at Ecas then about the jets.

I'm not sure which carburettor the car has though actually, I've not changed it though so it's whatever was original.

My garage is a great little Citroën specialist that I've used for years, but sadly their 2cv expert has retired and increasingly they are saying they unable to sort the Deuche. Shame really.
Author:  AZL57 [ July 20th, 2015, 9:44 pm ]
Post subject:  Re: Juddery acceleration on half throttle
Had the same problem was caused by false air entering under the carb flange.
Author:  Ianredspecial [ July 20th, 2015, 10:06 pm ]
Post subject:  Re: Juddery acceleration on half throttle
Hmm it looks perfect but perhaps I should take it off for a proper looky.
Author:  lpgo [ July 20th, 2015, 10:53 pm ]
Post subject:  Re: Juddery acceleration on half throttle
Ianredspecial wrote:
Hmm it looks perfect but perhaps I should take it off for a proper looky.


Put some sealant to both sides of the spacer when taking it off. it can make the diffrence...
Author:  ken [ July 21st, 2015, 1:05 am ]
Post subject:  Re: Juddery acceleration on half throttle
...or just file the base of the carburettor flat, to cure distortion which will have been caused by the nuts having been overtightened? ;)


lpgo wrote:
Ianredspecial wrote:
Hmm it looks perfect but perhaps I should take it off for a proper looky.


Put some sealant to both sides of the spacer when taking it off. it can make the diffrence...
Author:  Ianredspecial [ September 23rd, 2015, 9:35 pm ]
Post subject:  Re: Juddery acceleration on half throttle
Oh, I missed these two last replies, sorry.

Any hoo we put in the jet recommended by Ken, I got a new gasket/block too just in case. The float level was wrong too.

It is definitely improved, still a slight judder discernible but it's such a tiny wee motor I'm sure it's just normal now. It's a joy to drive to be honest once it's warmed up.

Thanks for all help, as always :-)
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