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 Hi again and carb backfire 
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Firing on two.

Joined: August 17th, 2010, 11:47 pm
Posts: 194
Location: Chichester West Sussex
Post Re: Hi again and carb backfire
Also the carb looks black inside !

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1972 dyane4 435cc


June 4th, 2018, 6:24 pm
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Firing on two.

Joined: August 17th, 2010, 11:47 pm
Posts: 194
Location: Chichester West Sussex
Post Re: Hi again and carb backfire
She’s a 24/21

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1972 dyane4 435cc


June 4th, 2018, 6:27 pm
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Firing on two.

Joined: August 17th, 2010, 11:47 pm
Posts: 194
Location: Chichester West Sussex
Post Re: Hi again and carb backfire
[url][URL=http://s341.photobucket.com/user/geoffsmith007/media/Mobile%20Uploads/IMG_4299.jpg.html]Image[/url]Imageurl]

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1972 dyane4 435cc


June 4th, 2018, 7:02 pm
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Agony Aunt - You have a car problem? Speak to Ken

Joined: March 6th, 2009, 1:40 am
Posts: 3675
Post Re: Hi again and carb backfire
That will be the backfiring... ;)
Anyway, it's a good old 21-24, so you'll need a 127.5 primary petrol jet.
The original was listed by Citroen as being a 120 or a 125, but most RHD cars with this carburettor had a 120 fitted, in my experience.

p.s. 21-24 is the correct description, since the primary choke should be listed first, if I'm not mistaken.

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June 4th, 2018, 9:24 pm
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Firing on two.

Joined: August 17th, 2010, 11:47 pm
Posts: 194
Location: Chichester West Sussex
Post Re: Hi again and carb backfire
Thanks ken

Just been out and checked the points gap and timing again, all spot on well as best as i could get it within 1 tooth, timed static after points gap set then around to the 43rd tooth and the light went out past it so adjusted the points gap to the light went out on the 43rd tooth then rechecked the static tdc and it had moved so adjusted points box to accommodate went back to number 43 and was within a tooth so good enough, think its slightly better but i still had a misfire and instant hesitation, maybe I'm expecting to much from the car its 1972! ill get a larger jet, i looked at the injector pump and it looked to be working ok i lubed up the mechanism and manipulated it by hand and used the wd40 on the pivot points but I'm reasonably new to this so not sure when the pump should work or if its adjustable on the rod/cam assembly.. i sops the next thing it to recheck the tappets AGAIN :shock: i think i will get the larger jet and take it from there.. thanks again for all your help :D

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1972 dyane4 435cc


June 4th, 2018, 9:57 pm
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Firing on two.

Joined: August 17th, 2010, 11:47 pm
Posts: 194
Location: Chichester West Sussex
Post Re: Hi again and carb backfire
ecas only list a 125 or 135 and 2cv city worse any ideas where to source from?

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1972 dyane4 435cc


June 4th, 2018, 10:07 pm
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Firing on two.
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Joined: March 21st, 2013, 12:04 am
Posts: 1577
Location: Exeter, Devon
Post Re: Hi again and carb backfire
Consider checking for other air leaks as well :)

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If you can't fix it with a hammer, it's probably electrical (or, an electric fuel pump!) ....


June 4th, 2018, 11:57 pm
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Agony Aunt - You have a car problem? Speak to Ken

Joined: March 6th, 2009, 1:40 am
Posts: 3675
Post Re: Hi again and carb backfire
TC, the accelerator pump injects fuel into the carburettor as its lever is pushed forwards by that cam on the offside end of the primary choke's spindle.
Your first photograph has a good view of the of the lever with the roller at its tip resting against the cam. Open the throttle fully to see how the lever moves, if you're not sure.

All that's usually needed to start it working again after a layup is to pull the lower end of the lever forwards repeatedly until fuel starts being pumped through the nozzle.
For the reason(s) already mentioned, it's best to carry out this procedure with the engine running.

Note that a larger primary jet won't cure any hesitation/backfiring caused by a non-functioning accelerator pump.
.
I can supply a primary jet drilled out to 127 if the usual suspects don't stock them, however that's only on an exchange basis...

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June 5th, 2018, 12:10 am
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Firing on two.

Joined: April 20th, 2017, 10:55 pm
Posts: 107
Post Re: Hi again and carb backfire
That's a lot of goo around the carb. Are your valves seating properly?


June 5th, 2018, 8:17 am
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Firing on two.

Joined: August 17th, 2010, 11:47 pm
Posts: 194
Location: Chichester West Sussex
Post Re: Hi again and carb backfire
Hi all

Reet I think I have cracked it after a lot of cocking about and ken was right with the idea of the fuel injector pump I found out that the pump cam was worn and not doing anything until about 1/2-2/3 throttle so I fashioned a thin piece of metal with a better radius on it so the injector works from the off l, and no more flat spot or carb backfires.. at the moment (short test) so many thanks in advance , 2 more things for the oracles on here I will start in another thread. Many thanks

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1972 dyane4 435cc


June 8th, 2018, 7:18 pm
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