John,
Setting the carb covers in the correct position should make a difference. I
don't have my ZS book with me but the way the vacuum works in helping to pull
the air valve up is probably affected by the position of the cover. I've read
that air valves ARE matched to carbs so that could be a problem also.
First are you sure that the hex head is stripped? Can you see down the damper
tube? It may be that the needle has simply become unthreaded from the adjusting
screw. That happens if the adjusting screw is turned counterclockwise enough
turns. Take your old air valve and try pushing the needle up into the air valve
while turning the adjusting screw clockwise, this should rethread the needle to
the adjusting screw. Spray some carb cleaner on the needle both at the bottom
of the air valve and down the damper tube. The needle may be gummed up and very
difficult to move up and down (sound familiar TOM DI IULIO?). Hopefully this
will work and you can use your old air valve.
If the hex head is truly stripped then you can try what I describe below, since
I think that you really need to use your original matched air valve.
I would take the adjusting screw and spider washer out of your "new" air valve
and put them into your old air valve. The trick is you have to get that
adjusting screw to turn loose of the needle (unthreaded from it) before you can
remove the needle and then drive the adjusting screw and spider washer out (more
on how to do that later). You have to somehow try to turn (counterclockwise as
you look down on it) that adjusting screw without concern about ruining it
and/or the spider washer, e.g. by using a drill bit/ and an extractor or
forcing a flat blade screw driver into the adjusting screw or maybe a Philips
head so that it turns. Oh and you have to do this without scratching up the
inside of the damper tube. You'll have to use plenty of force downward on the
adjusting screw and you might want to spray both ends (needle and down the
damper tube) with penetrating oil. Once you've turned the adjusting screw
counterclockwise enough (5-6 full turns should totally unthread it from the
needle), you can try to take needle out of the air valve. Remove the brass
screw out of the air valve that is holding the needle in position...it's a
little bitty screw 90 degrees to the needle on the side of the air valve.
You'll need a jeweler's screw driver or a real small blade screwdriver to get it
out. Pull on the needle, hopefully it'll come out. You may need to put the
position screw back in and try turning the adjusting screw some more if it
hasn't totally unthreaded.
Once you get the needle removed take a 1/4 inch steel rod at least 6 inches long
(you can go to Ace Hardware with your air valve to match the right size up with
the hole) and drive the adjusting screw along with the spider washer back up the
damper tube. It takes a fairly good whack but make sure your hold your finger
over the end of the damper tube or the adjusting screw and spider washer will go
flying, not that you're going to need them since you're replacing them with your
new ones. I've also used an unsharpened pencil to drive them out but I've also
had the pencil splinter on me too. A rod is safer or even a wooden dowel.
Before you replace the adjusting screw I'd get some new o-rings (viton o-ring
2-010). Call a bearing/seal dealer, they should have these. Viton resists
hydrocarbons well and keeps your damper oil from leaking out longer. Mine are
holding like champs. Ask for that material and size of o-ring. Spray some
silicone lubricant in the damper tube and on the adjusting screw with the new
o-ring, put it together with the spider washer at the top of the damper tube and
drive them both to the bottom (make sure it's all the way to the bottom) at the
same time. Put the needle and the position screw back in, set your needle flush
to the bottom of the air valve (I also start with a half turn to rich too, which
is 1/2 turn to the right clockwise looking down on the top of the air valve).
Give that a try.
Don't know about the 12 and 13 numbers on the air valves.
And good luck.
Bud
6's
4's
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