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Imposible down the idle with zenith 28IF

D

Dobbie

Me gustan los clasicos...
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Hi all.
Two weeks ago ,dismount , and clean with patrol , the carburetor of my R4 TL 1990. a Zenith 28IF.

Well the carburator was cleaned very well, all, and i put a new carton on it. All ok.
When i was to put on the engine, and start it, was imposible down the idle to 700 rpm . only was on 800----850. extracting the idle screw at maximun it was imposible down for 700 rpm...

what about it??? about this piece?, i have not this stopper.



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Last edited:
Have you checked ignition timing? If advanced it will raise idle speed.
 
That raised 4 sided castle like piece should have a steel cup or cap over it, yours appears to be missing.

it should be held in place by a small rivit, it looks like that is still there but you are missing the cap

Mike
 
Air leak...

Can't get the idle down - classic sign of an air leak.

If air can bypasss the butterfly you can close it down all you like, it won't have any effect on idle speed.

Charliemouse.
 
What is the gasket like inside the 28if? did you fit a new one? Only i have had a few of these split and cause problems, or check that the bottom of the 28if is flat by sitting the carb on a flat surface, ( check to see if it is like a banana) I have had to machine a few flat before.

Mike
 
Hello.
Yes, of course i think that the last friday, when i went to the gas-station, to clean the entire engine, perhaps with the presure of the hot watter, the " Cup" was forgotten. problems, by i think that for this hole i haven,t an air leak, or is posible, have an air leak for this hole?

By the way perhaps any air leak?, what can i verify it?

The gasket that i put on the 28IF was home-made, with material for it. I have an oil paper about 0.8mm for gasket. Perhaps this is the problem....?

Other way... This classic car it,s new on my. I bought it one month ago. It have 20 years, it,s from 1990. It,s a Renault 4 TL 1108cc.


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About the ignition time, i have a DIGITAL LIGHT STROBE to do it, but i the strobe at 0º and the signal on the engine mark 10º ??? if i put 10º on the strobe, i lose the mark on the wheel.. Tomorrow i put some pics about the ignition time, marks, and more.

Thank you very much for reading, and more for help me..
 
I think you need to fit that cap, i am not sure as to what it exactly does perhaps Malcolm knows?

I also think it would be worth buying a new gasket and fitting it rather than a hone made one, because there is only a tiny piece of gasket between the jet and the venturi, which if split will leak air (been there)

This might help too http://www.google.co.uk/imgres?imgu...enith+28if&um=1&hl=en&sa=N&ndsp=20&tbs=isch:1
 
The yellow arrow indicates where all of my air leaks came from.
 
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    28if carb.jpg
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oh, yes, the yellow arrow, i remmember last saturday when i made the gasket, y cut lot on this point. Next saturday, i take off the carburetor again, and made a new one, take some pics...

This morning i check the ignittion time, with my strobe, and it was on 1º only, near 0º PMS.. well i did put on 4º, and now the car goes better, but the idle is the same 770-800, and imposible down... i think that i have an air leaks on the gasket, sure....

here is some pics, from this morning

ignition time at 4º i Think on my R4 TL 1108cc
DWELL 62º.50



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and thisd is the oil paper for gasket that i use. It,s valid???



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Hi there Dobbie, just a thought, have you checked the emissions pipeing on your carb. Any splits can cause air to be sucked in and can cause increased tick over.
 
Hi there Dobbie, the plastic T shaped pipe at the top of your carb can become brittle with age (all that heat), and crack. The mod I did was remove it and blank off the pipe below the carb and plug the metal tube where the plastic T was. I then fitted a length of rubber hose to the rocker- box and ran it down to the chassis. A bit of oil vapour will help to rust-proof it! The ideal tick-over or idle speed of your engine should be 650 rpm.Hope this works for you.
 
Hi ,your problem seems to be common to old zenith 28 carb. mine too . ok what i plan to do is to swap to a weber32icev which i bought at low price from a friend. i already have made the conversion plate,but not yet install it.i wonder what will be the consequence ?will it be better
 
Hi again.
this morning i checked my carburettor with a Gunson gastester, and it show me 0,1 of CO2, perfect, and the color of the spark plug is correct, but the tick over it,s 850 - 900rpm. imposible. the problem is the gas-butterfly too old. I need a new butterfly to change it. all thanks, and happy new year....
 
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