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What's this thing on my carb...
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Author:  Devils Advocate [ July 22nd, 2010, 3:29 pm ]
Post subject:  What's this thing on my carb...

and why doesn't my Haynes manual make any mention of it? :(


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I think I've seen it 'pulse' back and forth during cranking, and it looks as tho' it acts on the choke lever (or, more likely, the choke lever acts on it when engaged), but what does it do?!

Ta much

Author:  toomany2cvs [ July 22nd, 2010, 4:32 pm ]
Post subject:  Re: What's this thing on my carb...

Devils Advocate wrote:
I think I've seen it 'pulse' back and forth during cranking, and it looks as tho' it acts on the choke lever


Yup. As vac rises, it pulls the choke off a bit.

Quote:
but what does it do?!


Fall off, mainly - and it makes such a horrible noise when it gets stuck between block and flywheel.

Author:  Tim2cv [ July 22nd, 2010, 5:19 pm ]
Post subject:  Re: What's this thing on my carb...

yes... it drops off

Image

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I cleaned the area and stuck gaffa tape over it... works fine!

Author:  Sean [ July 22nd, 2010, 6:35 pm ]
Post subject:  Re: What's this thing on my carb...

Its actually quite usefull given that many people dont know how to work a manual choke

it saves " over choking" your car when cold starting

older cars had a 2 stage choke which you had to hold the knob to get full choke and it returned to an intermediate stage of its own accord

Sean

Author:  Devils Advocate [ July 22nd, 2010, 8:37 pm ]
Post subject:  Re: What's this thing on my carb...

Toomany & Tim - what a double-act! :lol:

Thanks, folks. Well, I'd never have guessed. Pretty clever.

Cheers.

Author:  ken [ July 22nd, 2010, 10:21 pm ]
Post subject:  Re: What's this thing on my carb...

Not really that clever, as most of the 'choke pull-off' devices which haven't fallen off won't be doing much other than allowing air to leak into the manifold.

The diaphragm was riveted directly onto the end of the operating rod, which tends to hammer itself apart in service.

When that happens, the device is just some useless scrap metal screwed onto the top of the carb. :roll:

ken.

Devils Advocate wrote:
Well, I'd never have guessed. Pretty clever.

Cheers.

Author:  Jonathan [ July 22nd, 2010, 11:11 pm ]
Post subject:  Re: What's this thing on my carb...

Would that cause a lean mixure then? If so, would it be enough to cause 'pinking' at full throttle?

ken wrote:
other than allowing air to leak into the manifold.

Author:  ken [ July 22nd, 2010, 11:19 pm ]
Post subject:  Re: What's this thing on my carb...

Nope,
because manifold vacuum is highest at tickover or on the over-run.

First port of call when addressing pinking/pinging would be to check for too much ignition advance.
A weak mixture, plugs with too hot a heat range and so on would be lower on the list.

ken


Jonathan wrote:
Would that cause a lean mixure then? If so, would it be enough to cause 'pinking' at full throttle?

ken wrote:
other than allowing air to leak into the manifold.

Author:  Jonathan [ July 22nd, 2010, 11:24 pm ]
Post subject:  Re: What's this thing on my carb...

T'is on 123 which is retarded. The engine has done 193,000miles and has never been taken apart, so could it be coke build-up?

Author:  Devils Advocate [ July 23rd, 2010, 4:51 pm ]
Post subject:  Re: What's this thing on my carb...

I'm guessing that's possible, Jonathan - glowing carbon deposits could ignite the mixture as it's compressed even before the spark itself fires. Does the engine also 'run on' after turning off the ignition?

Has the ignition timing and points gap been checked? Always go for the obvious causes first.

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