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Carb settings

R

Rene LHD

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Suffolk
Good afternoon gents, RENE here, can anyone help me with the basic carb settings for mixture on my 845cc 1974 lhd R4.
I have set the mixture screw at 3 turns out as per the Haynes manual. Car starts on the button, and ticks over fine. When road testing, the car misfires and hunts badly. I have tweaked the screw by 1/4 turns to 4 turns out, car smells less of unburnt fuel but still feels like it is going to cut out, and screw feels loose in carb body. Removing the airfilter made no difference to the running. Any help would be gratefully received.
Rene
 
Are you certain the problem's with the carburettor? Is the ignition set-up correct? A mis-fire under load can sometimes be a sign of a failed or failing condenser. As you're smelling fuel it could be because the ignition's not fully burning the it and a failed condenser can cause a weak spark. What's the state of the plugs?
 
Will check plugs and spark and report back, but the points,condenser and plugs were all replaced last November. Carb has had new gaskets and float valve fitted, and cleaned up. Thanks for your reply Andre
 
There is a company called Carb Care in Lichfield who completely refurb a carb and set it up as original, like new.
 
The carb looks like a Zenith 28IF - the one that most of our cars have.
As you've taken the top off, it'd be worth taking the whole carburettor off and blowing through the main and idle jets (a footpump with a fine nozzle works well if you're careful). Make sure that the long tube (blue arrow in 2nd photo) is clear (yours looks a bit bent); you can do this with a long piece of soft electrical wire. Same for the passageways in the bottom part of the carb (they look a bit crusty in the photos). Use plenty of carb cleaner as well as air to flush through these and the filter in the 'doorbell' (yellow arrow in 2nd photo).
One other thing - it looks as though you've removed the spring that goes from the accelerator cable plate to the inner wing. When it's in place, the whole thing should look like this:
1742921532421.jpeg
1742921587562.jpeg

Good luck with it!
Lots of info here:

Démontage et réglage du carburateur Zenith 28IF

Démontage et réglage interne d'un carburateur Zénith 28 IF monté sur certain modèles de Renault 4 (entre autres...)
www.la4ldesylvie.fr www.la4ldesylvie.fr
 
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