Message text written by Dale VanCleef
>The reason that my mechanic said I needed the air valve assembly was
sort of strange. He said it had a hole in the bottom which was allowing
the damping oil to leak out. The hole, he said, looked perfectly
round... like it had been punched through. In any case, the carbs don't
dampen evenly because the front one runs out of oil so quickly. He gave
me a diagram of the carb and the part. To me, it looks like the slide
in a motorcycle carb. I found the part in the Roadster Factory
Catalog. Under the "number required" column it said "NSS" (not sold
separately?).
<
Appearently your mechanic is not very familiar with the subtle details of a
ZS carb. Thes carbs have adjustable needles and they are adjusted via a
screw in the bottom of the dashpot. There is an O-Ring seal that seals the
adjuster to the bore in the air valve to prevent the oil from leaking out
but after 31 years these O-rings loose resiliance. What you need is a new
O-ring. O-rings are included as part of the rebuild kits.
To change the O-ring you first remove the piston (air valve) from the carb.
Then you undo the the screw on the side that captures the needle then turn
the adjuster to release the needel and withdraw the needle. Next, find a
piece of dowel rod that will fit into the bore and use it as a drift to
push the adjuster mechanism out the top of the damper bore. Note that the
adjuster is held in place by a clip that will resist this action. When you
reach the end of the bore be sure to capture this clip and do not loose it.
Once the adjuster is out of the bore you will see the O-ring. I had one
that looked to be of graphite and crumbled when I attempted to remove it.
R & R the O-ring and reinsert the adjuster into the bore followed by the
clip and use the dowel to press it home. Reassemble the needle and the
needle retaining screw and reinstall the piston in the carb.
Repeat for the other carb since its O-ring is probably in almost as bad
shape.
Note that this is unique to the adjustable needle Z-S carbs. The fixed
needle Z-S and the SU's do not an this adjuster and no need for the dashpot
bore to go all the way through the piston and it is quite understandable
that an SU expert would be unaware of this O-ring if he were not familiar
with Strombergs.
Or send the carbs to Joe Curto.
Dave
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