Weber carb problem

[danny_nelson]

Re: Weber carb problem

Hi Mike,
I dont mean to keep this going, and I hope you are sorted now, but a burnt HT lead that is shorting out would perform erratic throughout the rev range.

[gouldsborough7]

Re: Weber carb problem

Just to keep this saga going a little longer, the new carb (Weber 32/36, not 28/36 as I showed earlier) new HT leads, dizzy cap and rotor arm, all contributed to the engine re-starting without too much bother.

There are a few fine-tuning snags still to overcome, and also the operation of the manual choke knob. On this carb, the choke mechanism does not increase the revs until the knob is 3 inches out of the dashboard, and the choke flaps are nearly closed. Whereas, in my experience of previous manual-choked cars, the extra revs came when the choke knob was pulled out less than an inch. At present, until the engine is fully warmed up, on the choke the engine runs slowly and lumpy. I am in the process of consulting the guy at Fast Road Cars about this, but am thinking I might swap over my home-made fittings from the old carb, where I ended up with 2 choke knobs - one for revs, the other for mixture. This worked very well, and with practice allowed me to juggle the revs versus mixture settings with a cold engine.

Liz, how do I arrange for a calendar? After the recent outlay on my Berli, I can just about afford £8.

Cheers
Mike

[macdonald.dm]

Re: Weber carb problem

I think I'm stating the obvious here, Mike, but when you pull the choke cable to close the choke flaps, doesn't this ALSO operate the throttle cam via an adjustable screw?

Certainly, the way the choke control should work - as I understand - is that the first half inch or so should ONLY increase the fast idle, and a further pull starts to apply the actual choke itself.

I'd be very surprised if there wasn't a rotating cam you could tighten the throttle screw against.

[lizbillings]

Re: Weber carb problem

Hi Mike. Send a cheque for £8 payable to Marlins Owners Club to my address inside front cover of mag and it will be sent off to you. Regards Liz

[gouldsborough7]

Re: Weber carb problem

Hi Donnie
Yes, you/I would expect an adjustment of screw against snail cam, but it hasn't got one! There is an inter-action between a lever operated by the choke cable to a thin metal stud, on which I had to dob some copper-ease grease to make it work more smoothly, but no actual adjustment. When I flagged this up with the guy at Fast Road Cars, he accepted the shortcomings and said something about the relationship between revs and mixture being set up at the factory. He promised a call back with conclusions about how to set up the carb.

I'll experiment further before I take the plunge and convert the mechanism to a 2 choke knob Mike special, as I did with the Grannie carb (for a different reason). No doubt I will summarise this on the site, and might establish a record for the most messages on one subject!

Thanks Liz, I'll send a cheque in the post.

Cheers
Mike

[lizbillings]

Re: Weber carb problem

Hi Mike. Remeber to put your address in too! Thanks. Regards Liz

[Dane_Rescueman]

Re: Weber carb problem

Hi Mike,

I have my old 32/36 sitting on my bench at the moment. When the choke is selected a small pathetic cam rotates. Upon pressing the throttle, a pawl moves out of the way and the Choke butterflies close. Upon releasing the throttle an adjustable screw stop sits on the cam thus holding the throttle open a trifle (an adjustable trifle nevertheless). As the choke is gradually released the choke butterflies open once the throttle is used. The throttle stop rests on the little cam and raises the idle a bit. With choke fully off the adjusting screw is not affected by the, now low part of the cam, any more. I have Webcon's own manual choke conversion on this carb so others may differ. With my carb, despite pulling the choke cable out fully, no activation of the choke butterflies happen until the throttle is pressed and released. I will try to get photos of this if I can. Does your carb work like this Donnie?
Wait till you assemble and wire in your own EFi !

[Dane_Rescueman]

Re: Weber carb problem

First attempt at Photos!
First view is rear of my carb with manual choke conversion. The second is a picture of the fast idle screw. The third is the throttle lever showing the normal idle adjustment screw and the little choke cam.
As I said, the normal operation is:
Pull out choke knob
Push down and release throttle
start engine.
It worked every time and was a great improvement over the auto choke.
I hope it helps

[macdonald.dm]

Re: Weber carb problem

Hi Dane.

Yes, that's exactly how my manual choke works - but I thought that was a peculiarity of mine since I converted it myself for the cost of one choke cable! (Article in Pitstop about 2 years ago?)

Yes, I can pull out the choke (which, on my setup, rotates the whole autochoke bimetallic spring housing) but nothing happens inside until I touch the throttle - that lifts the screwed throttle arm from the stepped choke cam as you mentioned, and allows it to turn. Works a treat - the engine has never flooded, and I can push the choke fully home after around a half mile even in cold weather.

[macdonald.dm]

Re: Weber carb problem

Mike, I wonder if the lever on which this "thin metal stud" lives is meant to be gently bent to act further on the choke cam? (Not that I'm suggesting you do this until told!!)

[macdonald.dm]

Re: Weber carb problem

PS. Highest number of replies for any thread? No chance!!

(But I better stop answering just in case...)

[lizbillings]

Re: Weber carb problem

I seem to have black coloured engine oil in the top of the carb. Not sure how it would have got there. Anyone any ideas? (apart from needing a new engine) Liz

[gouldsborough7]

Re: Weber carb problem

The manual conversion kit I fitted to the Grannie carb was of the type that still needed a press of the accelerator to set the tickover and butterflies on the choke. However, the act of pressing the pedal squirted too much petrol into the manifold, and it was a toss-up whether the sparking plugs got too wet to fire the engine. So I ended up with a Mike G 2-chokeknob home-made conversion of the conversion. This worked fine.

Now that I have just fitted the new 32/36 carb, I found it strange that the 1 choke-knob operation only allowed the revs to be increased once the knob had been yanked out of the dashboard by about 3 inches. Anything less ended up with lots of rich mixture and no fast-speed tickover while the engine was cold. See pic 1 showing non-adjustable cam fitting on side of carb.

So I have just converted this to a 2 chokeknob arrangement, which much simpler to do than on the Grannie carb. I just had to remove the cranked rod and fittings joining the choke mechanism to the that linked to the accelerator. Then made up a bracket into which the end of the additional chokeknob cable would fit. After which I attached the cable to the revs mechanism, and Bob's your uncle! I can now control the mixture and revs independently with a cold engine. The 2 chokeknobs on the dashboard are installed symetrically, and look OK. See pics for the conversion.

Cheers
Mike

[gouldsborough7]

Re: Weber carb problem

Just realised that the site has juggled the pics in the wrong order. The 2 pics (from left to right) are the new 2 chokeknob installation. The pic on the right was the 1 chokeknob view.
Mike

[macdonald.dm]

Re: Weber carb problem

Mike, on the 'one cable' pic on the right, the cam on the choke 'lever' seems to be acting against a metal stud - presumably the one you were referring to earlier? Does this 'stud' act on the throttle butterfly? Would having this 'stud' sitting closer to the choke cam therefore solve the problem? As you said, it doesn't look adjustable, but surely it's meant to 'do' the job - somehow?!

Hasn't the company got back to you yet about this?

You are absolutely right about how it SHOULD work; pulling the choke knob out the first half inch or so should ONLY increase the idle speed by cranking up the throttle only. A further 'pull' should then start to close the choke flap along with further increase in idle speed.

You obviously know what you are doing - and your chosen solution looks neat and well executed - but it just shouldn't be necessary!

Since converting my 32/36 to manual choke, pumping the throttle to 'set' the choke has never threatened to flood the engine - in fact I usually pump the throttle repeatedly when the car has been sitting for a week or so just to get it to fire more quickly! I suspect your previous - oversized! - carb was more susceptible to flooding.



Liz, the 'oil' in the top of your carb is possibly due to oil vapour being drawn from your crankcase by the 'breather' pipe? Does this pipe go to the air filter housing?