Well, yesterday I finally got the mixture adjusting tool for the
Z-S CD175's in the TR-6. I already had a Colortune and Unisyn, so
I thought I'd see about leaning out the mixture a bit (you could
often smell the gas in the exhaust). I hooked up the Colortune,
and as I expected the flame was very yellow at idle. Here's where
the fun begins. I start turning the mixture control to lean it out,
and I keep turning, and turning, and nothing happens. 20 turns or
so and nothing happens. 5 or 6 the other way and I'm back to the
stops at full rich. I guess I must have unscrewed the control all
the way. So, is the fact that the mixture control doesn't seem to
have any effect indicative of carbs that need to be rebuilt, or is
it something mode insidious than that and maybe I should try the
pair that are in the trunk from the parts car.
Presuming that you have the adjustable needles (not all Z-S carbs have
the adjustable needles, and there are a zillion different needles avail-
able...), I recall that the "adjustment range" is rather small, suitable
for final fine tuning, and not much else - the major mixture setting
would come from gas [float] level . . ., which is of course much less
convenient to set! At idle, I suspect that the idle-air adjust screw
will have much more effect than mucking about with the main needle (that
was the apparent case with my old Europa).
Finally, note that if you truly "unscrew" it all the way, the needle can
fall out of the piston . . .
-RDH
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