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Flat spot on pick up - S/D Zenith...

One of the cars has an annoying flat spot on pick up, it is a standard 1935ish S/D Zenith the jets are the correct size so far as I can tell and it is stamped 7 on the flange.

The bowl and body are the correct type to be matched together.

The carb appears to have had some work done to it but is unknown to me.

Any suggestions for improvement please?

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Re: Flat spot on pick up - S/D Zenith...

You have probably checked already for a worn spindle?

Location: Wales

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Re: Flat spot on pick up - S/D Zenith...

There is slight wear in it Ian - I was going to cover the ends in thick oil and see if that improved things...

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Re: Flat spot on pick up - S/D Zenith...

Certainly sounds like a hint of weekness, as you will be well aware the cause could be wear or blockage. Have you tried a slightly larger compensating jet?

Location: NZ

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Re: Flat spot on pick up - S/D Zenith...

I am going try a larger compensating jet today Ian - thank you.

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Re: Flat spot on pick up - S/D Zenith...

R,
Have you taken off the emulsion block to see if it's clear?
Dave.

Location: Sheffield

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Re: Flat spot on pick up - S/D Zenith...

Thanks Dave - I had a good look at that and it 'appears' clear.

I appear to have resolved it by changing the float bowl using the original jets.

For information, I initially fitted a 65 compensating jet that cured the flat spot but caused a misfire up the revs (??).

Thanks for all your suggestions!

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Re: Flat spot on pick up - S/D Zenith...

It could be the tiny little jet underneath is blocked. This jet is often forgotten.
Vince

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Re: Flat spot on pick up - S/D Zenith...

Where is the oft forgotten tiny little jet please Vince?

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Re: Flat spot on pick up - S/D Zenith...

Hi Ruairidh

Its on the Cornwall website http://www.austin7.org/Technical%20Articles/Carburettor%20Jet/default.html

It bleeds air for slow running but worth eliminating as a source of the problem

Happy tinkering

David

Location: The home of Hereford A7 club