This is in response to the people having problems with the damper oil
leaking. This was posted by Kevin Riggs awhile back:
At the base of the piston bore, a very small star clip captures a small brass
screw with an allen head (1/8th inch?). The screw has an o-ring (I forget if
it's at the head of the screw or around the tip) which seals oil in the dashpot.
The bottom surface of this screw bears on the head of the mixture needle.
The hole at the base of the piston sleeve into which the needle is inserted is
smaller than the mixture screw diameter--so the mixture screw cannot be removed
from the bottom of the sleeve. However, there is apparently a chamber between
the threaded portion of the piston sleeve and the needle's hole, into which the
mixture screw can be lowered; the effect of this geometry is that the mixture
screw can be turned down into this chamber without the threads binding, and
further attempts at leaning out the mixture
just twirl the mixture screw in this chamber without damaging either the piston
sleeve's or mixture screw's threads. When this happens, there is no discernible
change in the mixture screw's resistance to further adjustment; it just stops
moving the needle down.
Similarly, above the threaded portion of the piston sleeve, the mixture screw
can be loosened until its threads are clear of the piston sleeve's threads, and
yet remained captured by the star clip. And again, you can't really feel when
this happens.
Bad ASCII Art Warning: My mailer uses proportional-spaced fonts, so this is
likely to look awful on your machine. Sorry. If you can read it at all, this
figure should show a cross section of the piston bore. The mixture screw is
shown in the center of it's travel.
===== <-- Star clip
| |
| | <-- empty space to hold mixture screw
| | in full-rich position
< < > >
< < > > <-- Threads in piston bore < < > >
| | | |
| | | | <-- empty space to hold mixture screw
| ---- | in full-lean position ---- ----
|
| <-- Needle fits here | |
Looking down the bore of the piston sleeve with a bright light, you should be
able to see the allen-head slot of the mixture screw. You might make out
the star clip around the rim of the bore, though I find it hard to see.
With the piston out of the carb, I think you'd find it easiest to fit your
mixture-adjustment tool into the bore of the piston if you remove the retaining
sleeve first. The purpose of the retaining sleeve on the mixture adjustment
tool is to lock the piston into alignment with the carb body as you turn the
mixture screw, thereby preventing the rubber diaphragm from being twisted and
torn. However, on my tool, the allen key is slightly warped, making it
difficult to engage in the mixture screw with the retaining sleeve in place.
With the piston out of the carb, the rubber diaphragm is out of harm's way, and
you can safely set the retaining sleeve aside.
Once the mixture adjustment tool is engaged in the mixture screw, you can
tighten or loosen the mixture screw all day long, but it will remain captured
until you remove the star clip above the mixture screw. This is best done with
a dental pick. If one is not available, you might try the smallest crochet
needles sold at K-Mart ($1.50. I bought the whole 6-tool set for about $5, just
to be sure. Then I found a dental pick...). With a small hook, the star clip
is quite easy to withdraw; without a small hook, it's a royal bitch. Once the
star clip is out of the way, remove the mixture screw by turning it clockwise
(it's reverse threaded).
All of this information is useless if Larry's right and you have a
non-adjustable carb; but maybe Larry's wrong and you've overlooked the mixture
screw at the base of the piston bore.
Best of luck, and I apologize if my writing's tedious; I'm trying to help, but
this stuff is tough to describe.
Bruce_Harding@ccm.hf.intel.com
57 TR3
66 TR2000
75 TR6
70 Austin Mini Cooper S
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