Maybe I'm reading your post wrong but it sounds like your trying to adjust
mixture to get the carbs synced. Loosen the throttle linkage clamp bolt to
one carb and turn the idle screw on one or the other carb to synchronize
using a piece of rubber hose or a Unisyn or similar. Then retighten clamp
bolt and recheck.
The normal starting point for the jets is to have them flush with the bridge
(remove vacuum chamber <dashpot>, spring and piston with needle to see
better), then back off jet nut 12 flats (2 turns). Jet should be approx.
.060 down from bridge. Reassemble.
Type of needle you may need is very subjective (your altitude, what mods
you've done to engine, etc.). If the car was running good before and you
just wish to replace needles you should find the needle size stamped on the
upper end of the needle in very small print.
Rebuild yourself? Sure, if you feel you have some mechanical ability and a
good manual to guide you along. Also there is at least one good video
available for rebuilding SU's if you prefer that.
Mike
'79B (SU converted)
----- Original Message -----
From: "William T Snyder, II" <wtsnyder@juno.com>
To: <mgs@autox.team.net>
Sent: Sunday, July 01, 2001 10:20 PM
Subject: Carbs
> Hello list. I have a '66B with an earlier 3-main engine fitted with
> original SU carbs. I recently tried fiddling with the rich/lean
> adjustment using an SU synchronizer tool. I now have the car running best
> with both jet-adjusting nuts fully tightened and I still don't have full
> synchronization. The car starts well (please don't strike me, Prince of
> Darkness!).
>
> Does this mean that I need new needles? If so, how do I determine which
> type, and where does one start to retune from scratch? What signs
> determine that the carbs are in need of a complete rebuild, and is this a
> job to be attempted by a neophyte (i.e. me)?
>
> Thanks in advance for your answers.
> Bill Snyder
> '66MGB
> '72BGT
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