Bud:
A bit of clarification here; The anti run on (or "vent") port is
designed to have a vacuum applied to it, not pressure. If you can get
air to come out the fuel line port, it is because the needle valve is
open and permitting air to flow back out the fuel line.
Let's review all the openings to the float chamber:
1. Fuel line, via the needle valve which is controlled by the
float;
2. Vent port via a vent valve, which is controlled by the
throttle.
3. Fuel jet, which is controlled by the metering needle on the
air valve.
The air valve is in turn controlled by engine vacuum.
4. Starter valve port (choke), controlled by the choke knob on
the dash.
Under normal operating conditions at idle;
1. Fuel line is closed by the needle valve (because the float
chamber is full of fuel)
2. Fuel jet is barely open, as the air valve is barely raised
off it's seat.
3. Vent port is open to the carbon canister, which is at
atmospheric pressure.
4. Starter valve port is closed.
Under normal operating conditions at cruise;
1. Fuel line is closed by the needle valve (because the float
chamber is full of fuel)
2. Fuel jet is open with the air valve raised off it's seat.
3. Vent port is open directly to atmosphere via the vent valve.
4. Starter valve port is closed.
When the engine is shut down;
1. Fuel line closed
2. Fuel jet barely open, (air valve is still slightly raised
because of residual manifold vacuum).
3. Vent port is at manifold vacuum via the carbon canister and
anti-run on solenoid.
4. Starter port is closed.
This last state kills the engine because fuel cannot flow out of
the jet; Since the float chamber is at manifold vacuum, there is
insufficient pressure to push fuel out through the jet past the metering
needle.
The fact that you cannot blow through one of your carb vents
tells me that one of your vent valves is likely misadjusted. I cannot
say which one because you don't state whether the throttle is open, the
starter valve is closed, etc. The vent port can be either open or closed
depending on the position of the other valves, linkages, etc on the
carb.
To see how to adjust the vent valves, go here:
http://home.comcast.net/~v.navarrette/ and click on "TR6
Articles". I have copies of Nelson Reidels Carb overhaul articles
(wonderful stuff) posted here. I would send you to the Wayback machine,
but it appears to be down at the moment.
Cheers,
Vance
------------------------------
Cogito Ergo Zoom
(I think, therefore I go fast)
TR6 Web page: http://home.comcast.net/~v.navarrette/
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Aledotr6@aol.com
Sent: February 07, 2005 8:32 PM
To: 6pack@autox.team.net
Subject: Clogged Carb Port
On one of the ZS carbs, the anti run-on port seems to be clogged. You
can't
blow through it at all. On the other one, if you blow through it, air
will come
out the fuel line port, which makes sense, because it is supposed to
force
air into the fuel bowl stop the flow.
I've tied compressed air, and a thin wire and heavy monofilement in the
ports
to see if anything was obstructing it and nothing has helped. Could a
plug or
bushing be in too far, blocking the air flow? Any suggestions on what to
try
next?
Thanks,
Bud Trussell
Close to firing up the 75 TR6
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