Hi John,
Yes, they have to be perfectly centered for proper mixture. If they rub it
will cause three problems. First, your mixture will never be right. Second
it will elongate the hole in the nozzle thereby ruining it. And third, it
can cause the piston to stick instead of retuning all of the way to the
bottom.
The first thing that I would suggest is to inspect the nozzles. Remove the
four screws around the base of the piston dome. Lift off the dome and
remove the piston. CAREFULLY lift the piston straight up as the needle is
extremely fragile. Look down at the nozzle to make sure the hole is not
elongated at all. If all is well, reassemble in reverse order. BTW, if you
remove both pistons at the same time keep all of the parts together. The
pistons and domes are matched sets.
Checking for centering is somewhat awkward. The old "piston drop" method
will tell you if it is dragging the side of the nozzle. It will not tell you
if it is exactly centered. The best thing that I've found is a small
inspection mirror that will fit into the carb. A small dental mirror is
ideal. You can see side-to-side from the front. Front-to-back requires
lifting the piston and looking at the side view of the needle/nozzle with
the mirror. To adjust it, there is a large , thin nut above the mixture
knob. Loosing this will allow the nozzle seat assembly to slide around.
Getting the nut tightened without moving the nozzle assembly is something of
a challenge. Patience will persevere, however. Unless your luck is better
than mine, it will take several tries.
Best regards,
Fred Schroeder
'70 2000
SRL311-13359
TDROC
Home page http://home.texoma.net/~sitsinwest/
----- Original Message -----
From: "John Sugar" <jsugar@quiknet.com>
To: <datsun-roadsters@autox.team.net>
Sent: Friday, February 01, 2002 8:02 PM
Subject: S U Carb Needle Centering
> Do the needles on SU carbs have to be dead center in the nozzle? Mine
brush
> one side (marker ink on the needle rubs off). How centered should they
be?
> If they should lower without brushing, is there a simple way to center
them?
>
> I'd like to solve this, if it's a problem, before the weather warms up.
>
> John Sugar
> Sacramento
> 70 2000
>
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