Webers on My 2.0 Zetec - problems

[David Mirylees]

My Lotus/Caterham 7 with a 2.0 Zetec, running presently on a (possibly) mismatched pair of 45 DCOE's (45DCOE9 & 45DCOE16). Although the car has run well over the last 10 years since the transplant, (apart from acting as though it has a "pit-limiter" when off throttle) I have found that it is impossible to set the throttle adjustment screw as the motor "ticks-over" at 1100 plus without any throttle screw contact at all (pressure on the throttle lever will reduce the revs but it returns to 1100 or more as soon as pressure is released) with the result that it is almost impossible to tune them. (I have a strong return spring on the main lever and also on the twin cables)

 

I also note that the barrel on cylinder No.3 does not give any discernable "hiss" and my old crypton balancer gives a reading of 2 when all others are at 4.5, Also the idle screw, when removed, was of a black appearance as was the No, 3 plug. Regardless of this, when given some stick the beast still flies and examination of the plug immediately after a blast shows it as being relatively OK albeit a bit sooty. (can I say that?). My thoughts are that it is running rich on No.3 and I have checked the float level (15 / 8.5) and idle mixture screw a dozen times with no change.

 

By the bye, main jets are all 135; Idle jets are: 50F8; Emulsions are F.16.

 

Any helpful suggestions greatly appreciated (I have trawled back to 2001 - some interesting threads but couldn't find my particular problem) It's been a long time since I have had to play with these things...........................

 

Many thanks

 

david

[Normans_Ghost]

David, it sounds like one of the butterflys is out of alignment. I'm not sure exactly whet they're like so you may haev to modify the following slighly.

 

Remove the cars. Then slacken the throttle screws right off. Then slacken the 2 screws which go through the butterfly into the spindle. These may have split ends with one or both end turned out to stop the screw from dropping out. You should be prepared to replace these 8 screws (2 each choke).

 

Now with throttle fully closed seat butterfly to choke. Don't use any pressure, just gentley seat the tapered edges to the choke. Tighten screws and bend back ends. When this has been done on all 4 chokes refit carbs, turn throttle adusting screws to give some idle and balance air flow and adjust mixtures.

 

You can get any parts you may need from your nearest Webcon dealer (search google)

 

Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here

You and your seven to The French Blatting Company Limited

[Normans_Ghost]

Tried to ed and system thought it was a double post.

 

Ok, here's a link here. The screw is No. 35.

 

The picture's too small to see if it has split ends. If not I suspect the threads are squezzed in a pair of pliers when the screws are tightened. This is important as you don't want one of these coming loose and being sucked into the engine. (Which may have already happend hence reason for throttle not closing)

 

Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here

You and your seven to The French Blatting Company Limited

[allen]

Check that the venturi is still firmly in the correct position, I had similar problems and it was caused by one venturi having dropped down.

 

allen

[David Mirylees]

Thanks chaps - I'll get the carbs off and give the butterfly screws a good looking at etc.

 

One thing I am unsure of - how does one adjust the airflow?

 

I can adjust the balance and the mixture but I can see no airflow adjustment screw

 

Ref the venturi - it (they) appear OK and were all wired for safety when I put the engine in

 

cheers

[Big Brother]

You can balance the individual chokes by using the Air Bypass Screws.

These are found under a small white cap that can be prised off.

The screw itself has a locking nut fitted to it

 

They are parts number 25,26 and 27 in Norm's diagram

 

Steve

 

 

SE7EN-UP!

The difference between ignorance and apathy? I don't know, and I couldn't care less!

 

[alextangent]

It's worth cleaning out the affected carb first before dismantling it in an attempt to adjust the level of individual air-flow. The blackening might be idle blow-back caused by running too lean on that choke, causing fouling of the idle airway. Does that carb spit at idle? Carb cleaner and a straw (no, not for drinking it but to blow through the airways) may fix the problem; if the idle screw is that sooted, then the airways are probably sooted up too.

[David Mirylees]

OK, butterfly screws are fine. Butterflies are visually sitting at rest identically. Venturi are fixed and fine.

 

There are no air bypass adjusment screws on these old beasts - at least that appear anywhere that I have looked :-(

 

I am thinking now that the best way forward may be to let Gower & Lee take them both and rebuild them to match. It is beginning to sound as if they are just getting old with the gremlins that lurk dormant for so long waking up!!

 

Really frustrating when the basics of tuning cannot be applied. (I know, should have known better in the first place etc etc)

 

Very many thanks to all that commented.

 

cheers

 

david

[philwaters]

Did you slacken off the butterfly screws and see if the butterflys would settle any more happily? I remember changing mine once after knife edging the butterfyls to improve progresion and making a hash of fitting them back in. Top tip was to hold them up to the light and view the sliver of light that comes though. With no throttle stop you should get any light through them.

 

Phil Waters

[Normans_Ghost]

David, Gower & Lee. Used them 40 odd years ago. They should know what they're doing.

 

Did you try Phil's method?

 

 

Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here

You and your seven to The French Blatting Company Limited