Mike Mason wrote:
>
> O.K. folks! I am at my wits end. Rebuilt the two Zenith Strombergs on
> my TR6. Put them back together the way they were, when the shopmanuals
> were not really clear. (That's assuming that the DPO had them together
> correctly in the first place. It hardly ran when I got it, so nothing to
> compare to.)
>
> Thanks for the suggestions on the leaks. I have used about three
> thousand gallons of spray checking for leaks. No matter what I do, they
> idle at about 1600 RPM. All linkages unhooked, so can't be that. Last
> night the motor speed suddenly dropped. I don't know what I touched.
> Revved the engine a little and it returned to 1500 RPM or so.
>
> Everything looks clean and seems to function as it should. Put all new
> gaskets in with the rebuild. What am I missing, or should I just have my
> local Medicine Man come by for an exorcism?
>
> Thanks for any words of wisdom or solutions, no matter how
> off-beat...I'll try just about anything. I want this thing on the road!
>
> Cheers,
>
> Michael Mason
> Hi-revvin' in St. Louis
Michael,
I had a very similar problem with one of the ZS 175 carbs on my Stag.
When I first started the engine it idled nice and low, but after a minute
or two the left side carb just started flowing a lot more fuel and air.
If I placed my hand over the throat of the carb to shut off the air flow
and then removed my hand the engine would again idle fine for a minute or
so before revving back up. I had just rebuilt the carbs and replaced
everything and made sure the throttle plate was closing fully. Since the
right side carb was operating fine I started exchanging components but
the problem always stayed with the left. I also went to the local
Medicine Man and we did every voodoo dance he knew, but nothing helped.
Finally, I talked to a fellow named Joe Curto in the NY area (after
talking to a number of supposed ZS experts who knew nothing) and he said
it was the bypass valve on the side of the carb, the funny pointed thing
with a spring and diaphragm in it. I told him I had rebuilt it and even
switched the left side unit with the right one with no change in the
problem. He suggested to take the unit off and temporarily place a piece
of tape over the holes. If the problem goes away (as it did in my
case)it is the bypass valve. This valve is more of a pollution control
device and does not affect performance or driveability. To disable it
open the diaphragm and there is a screw inside. If I remember correctly
you back off the screw enough so that the diaphragm is forced to always
stay in contact with the carb housing and not open. In my case this
solved the problem. Good luck and if you have any further questions on
this procedure just let me know.
Dan Pruzan
71 Stag
Santa Clara, CA
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