Lee,
I have more questions than answers at this point.
Is it running lean over 2500 at full throttle (acceleration), part throttle
(cruising), closed throttle (deceleration)? What are the sensors showing during
those stages? There are the ever friendly emission devices that could be
factoring into the change in mixture at some of these stages.
Why do you suspect the needle?
Most of the needle that is below the shoulder of the needle, and thus below the
air valve, is in the jet assembly as far as I can tell. You should be able to
tell if your needle needs replacing by putting it on a flat surface and rolling
it while making sure the shoulder is in full contact with the flat surface.
Watch the point of the needle as you roll it, if it moves up and down it's bent
and should be replaced. You can also slide a feeler gage under the midpoint of
the needle while its on the flat surface and then roll it exactly halfway over
and check the gap again if they're equal then the needle is straight.
The needle doesn't rub against anything in operation so if it has wear that
shows or linear marks or scratches then replace it. The jet would also be worn
so replace it too since that's what it was rubbing against.
Bud 71TR6 CC57365
____________________Reply Separator____________________
Subject: Stromberg Needle Height
Author: "Janssen; Lee K" <lee.k.janssen@lmco.com>
Date: 10/14/98 6:37 AM
Yet another question that will go unanswered:
I'm running a TR6 with dual EGO sensors that indicate that I am running lean
above 2500 rpm. The solution is to either get a replacement needle or modify
the one I have.
The problem is this: How do I know which portion of the needle is actually
in the jet?
My first thought was to monitor the vacuum above the diaphragm which defines
the force trying to lift the carb piston. This force is offset by the spring
trying to force the piston back down. However, I cannot convince myself that
the Bernoulli forces acting on the bottom of the piston are negligible.
Another possible solution is to make a resistive sensor (10 turn pot, long
wire and a spring) to determine the piston position.
Of course the correct solution is to use a rolling dynamometer, however, it
seems just a little bit like overkill for such a simple (?) problem.
Thanks in advance
Lee Janssen
Denver CO
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