If you are using the standard Stromberg 150's, they do NOT have a an
adjustment nut that is externally adjustable (are you thinking of SU's that
have a lower jet adjusting nut?). The large nut under the float chamber on
the ZS's is a purely a plug.
The mixture adjustment is achieved by the use of the correct tool (looks
like a very long allen wrench, with a small locking tool that stops you
tearing the diaphram) inserted into the piston once the damper has been
removed. Not all ZSs are adjustable (and I don't know GT6's well enough to
tell you if they are fitted with carbs that are). For more info, the
Haynes, or Factory manual will give a good description, or the Haynes
"Weber, Stromberg and SU carb" manual is a vertible font of knowledge for
all Triumph owners.
>I tried to use my new ColorTune kit tonight on my GT6, but I couldn't budge
>the mixture control screws under the Zenith carbs. Does anyone know a safe
>way to loosen them so they can be adjusted?
>'67 Spitfire (soon to be a Spit 6)
>'69 GT6 (parts car)