> Date: Tue, 03 Jun 1997 21:47:55 -0400
> From: Sholtes IV <joeiv@concentric.net>
> To: triumphs@autox.team.net
> Cc: Mike Mason <mmason@lindenwood.edu>
> Subject: Re:Zenith help? (TR 6)
> Reply-to: Sholtes IV <joeiv@concentric.net>
> Michael Mason wrote:
>
> > O.K. folks! I am at my wits end. Rebuilt the two Zenith Strombergs on
> > my TR6.
>
> ~snip~
>
> No matter what I do, they
> > idle at about 1600 RPM. All linkages unhooked, so can't be that.
>
> ~snip~
>
> > 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
>
>
> Mike,
>
> You said ANY suggestions, so here you go. When I rebuilt the carbs for my
> TR 250, I had the same problem. After countless fiddling, I noticed that
>some-
> how the "by-pass valves" were at fault. Since I'm not going to be road worthy
> (I am not worthy, etc..:^) ) for a while, I just disconnected and plugged the
> vacuum lead to them, and my idle returned to normal. When I get everything
> painted and back together, I'm going to find out just what these things do,
> and what's wrong with mine...
>
> With just a small hint,
>
> JOE IV
> TR 250
> WALLINGFORD, CT. USA
> > Hi-revvin' in St. Louis
>
>
I have been reading about two problems with Zenith carbs lately. One
concerns idle not returning below 1600 RPM or so as in the problem
above. The other is idle problems when sitting in traffic as the car
warms up. I concur with the diagnosis above for high idle. Haynes
says "if the valve jams shut it is unlikely there will be any
symptoms. If it jams open the idle will be too fast, and there may
be apparent lack of engine braking." That is from the Haynes
Spitfire manual MkI, III, IV: 1962 to 1974, page 198. When I bought
my first '73 Spitfire in 1976 it would not idle below 2000. I read
that passage and one of the first things I did with the other four
Triumphs I have owned is to make a gasket to block off the by-pass
valve.
I was fortunate that with all my cars, except my present '73 Spit,
the PO's had not adjusted the temperature compensator. The only car
I can remember noticing the operation of the compensator was on a '76
TR6. In stop and go traffic it would idle up 100-200 rpms. The
increased idle would bring the temp down some and as it went down so
did the idle back to normal. Investigation showed that these
compensators would open more as the car got hotter in traffic. With
my current Spitfire the idle was terrible when warmed up and even
worse in traffic. Winter driving was not a problem even in traffic.
I did a lot of modifications to the cooling system (160 degree
thermostat, by-passed intake manifold cooling line, larger radiator
with electric cooling fan) with no improvement. I read the tech info
from VTR about setting the compensator to open at 140 degrees and set
mine as per those instructions. The result was even worse. The
Haynes manual, also on the same page 198, says "at low or medium
temps the valve should be shut....If jammed shut the rich mixture
will make itself apparent by a lumpy idle. If jammed open the weak
mixture may not be noticeable." If you set the valve to open at 140
degrees, it will never open. I set mine to just start to open at 40
degrees. Now my car idles at 850 rpm traffic or no traffic. The
only problem I noticed by jamming it open all the time is that cold
starts are a little more difficult. I found that it is desirable to
have it shut when the ambient temps are cooler and open by the time
the car has warmed enough to run without the choke. Your results may
vary...and I understand TR6's may vary from Spitfires but the carbs
on my GT6 operate the same as my Spit.
Hap
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