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Re: SU HS4 carb jet setting on 1968 MGB/GT

To: <Greg_Hutmacher@i2.com>, <mgs@autox.team.net>
Subject: Re: SU HS4 carb jet setting on 1968 MGB/GT
From: "Jeff Fayne" <fayne@attglobal.net>
Date: Thu, 31 Jan 2002 11:12:26 -0600
Hi Greg,

Here's a link to help you out, although written with a slant towards
triumph's, it still applies to the MG's:

http://www.vtr.org/maintain/carbs.html


As the bearing is raised (mixture adjusting screw screwed clockwise as
viewed from the bottom), the mixture becomes leaner. The needle, being
tapered, allows more fuel to flow (mixture richens) as the bearing is
lowered and the progressively thinner portion of the needle is exposed.

A good staring point for the mixture screw is 2 full turns (12 flats) out
from full lean.

The list's very own Lawrie Alexander (Lawrie@britcars.com)   (among others)
is a great source of SU related knowledge (as well as star of the Moss SU
rebuild video). I'm sure he would be open to answering the occasional email
or via posting to the list.

Also, Haynes put's out a nice SU manual (although disguised as a Weber Carb
manual) called "Weber Carburetor Manual, Including Zenith Stromberg and SU
Carburetors" ISBN 156392157.  I bought mine at the local PEP Boys, I'm sure
it's available ate Borders, Amazon, etc.

Good luck

Jeff
'70B



> On the SU HS4 carbs, looking at the height of the jet inside the jet 
> bearing, what is the relationship in terms of rich/lean mixture with the 
> jet higher or lower in its bearing?  In other words, as I adjust the jet 
> upward inside the bearing, does that make the mixture more rich or more 
> lean?  Is there a general wisdom on what height to start with for a 
> nominal mixture setting?  I'm about to put the carbs back together and 
> right now I have it flush with the top of the bearing.

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