Technical question for Zenith Carb experts...

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MajorBenz
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Model you own: w108
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Technical question for Zenith Carb experts...

Post by MajorBenz » Tue 21 Aug, 2018 12:10 pm

Hi guys, I Have a technical question for any Zenith experts out there:

I just finished rebuilding my front carb, and am running the tests prescribed in the workshop manual. There is healthy stream of fuel coming out the jet in stage 1 when I press on the pump. However, it is squirting straight down the throat, when the manual says the stream should be “hitting the venturi wall 10-15mm below the upper edge of bedplate”. I am hesitant to be bending that skinny little tube, and am wondering if I need to bother? Does it make a big difference to the way the engine runs?

Any advice greatly appreciated.
Cheers,
Dan
:)
Silver 1969 280S - "Grace"

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Bartman4800
300 SLR
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Re: Technical question for Zenith Carb experts...

Post by Bartman4800 » Tue 21 Aug, 2018 2:53 pm

You can bend that copper tube carefully, but only if you notice "pickup" problems.

Backfiring on acceleration.


Regards, Bart
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John Green
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Re: Technical question for Zenith Carb experts...

Post by John Green » Tue 21 Aug, 2018 9:41 pm

The accelerator pump and jet are only active for a very brief period of time when you "floor it". so if it drives fine, don't touch. It is an old delicate contraption.

Is there a specific reason for only doing the front carb? Depending on the condition of the rear one you may now have an engine that runs out of balance? As an example the secondary diaphragm in the rear one will be old most likely either slow to react, of have some degree of vacuum leak. If so the rear 3 cylinder will have a later response on the secondary?
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MajorBenz
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Location: Melbourne

Re: Technical question for Zenith Carb experts...

Post by MajorBenz » Tue 21 Aug, 2018 11:44 pm

John Green wrote:
Tue 21 Aug, 2018 9:41 pm
The accelerator pump and jet are only active for a very brief period of time when you "floor it". so if it drives fine, don't touch. It is an old delicate contraption.

Is there a specific reason for only doing the front carb? Depending on the condition of the rear one you may now have an engine that runs out of balance? As an example the secondary diaphragm in the rear one will be old most likely either slow to react, of have some degree of vacuum leak. If so the rear 3 cylinder will have a later response on the secondary?
Hi John,
Thought I'd tackle just one carb at a time as I'm still pretty new to this. And good to have 1 x carb still assembled as a reference for the one in pieces! I bought two rebuild kits. Sounds like I should a.) - leave jet tube squirting where it's squirting and b.) get cracking on the rear carb...

I keep waiting for you guys to have a clearance sale now your out of the spares game. Should I stop holding my breath?
Silver 1969 280S - "Grace"

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