Subject: Re: [TR] Slow idle drop

From: [email-masked]
Date: Mon, 7 May 2012 16:56:28 -0400 (EDT)

It is more likely to be the vacuum operated over-run valves.  They are 
mounted on the side of the carb next to the throttle shaft.  Their job is to 
open up with vacuum gets high enough to cause excessive emissions.  There is a 
diaghram inside and reacts to the vacuum and opens a valve against an 
opposing spring.  If the spring tension is set too low it will open prematurely 
and close slowly.

You can identify them by the small tower that extends straight out with an 
adjust screw in the middle.  The proper way to adjust these is with a vacuum 
gauge on the car so your rebuilder may not have been able to adjust them 
properly.  Try loosening up the lock nut and turning the screw in a half turn 
or so and see if that changes anything.

Good luck.

Dave

In a message dated 5/7/2012 2:39:53 PM Central Daylight Time, 
[email-masked] writes: 
> I recently installed professionally rebuilt ZS carbs on late TR6 engine. 
> I'm
> having an issue I hope to get some advice on.  After running at speed, say
> 2500 to 3000 rpm, and then coming to stop, the rpm is very slow to drop to
> normal idle.  I would say it takes about 10 seconds to settle down. The
> problem is also evident when up shifiting, as the rpm stays high between
> gears.  I have inspected the linkage and don't find that it is hanging up
> anywhere. Is it possible though that it could be something with the way I
> reinstalled the linkage?  Or could it be that the vacumn advance is not
> functioning properly, or????

** [email-masked] **

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From: [email-masked]
Date: Tue, 8 May 2012 08:34:51 -0400 (EDT)

Ed,
 
I'm assuming that your emissions equipment (air pump, gulp valve, etc.) has 
 been disconnected....if not, a big culprit behind the symptoms you 
describe  would be a faulty gulp valve.
 
Often,it helps to have the engine running when you check linkage adjustment 
 problems.  Have someone depress and release the accelerator pedal while 
you  observe the operation of the linkage.  Look around the individual carb  
throttle plate linkages very closely to be sure they're promptly returning to 
 their stops.  Once you've ruled out any linkage problems, remove the air  
cleaners and check operation of the air valves to be sure one or both aren't 
 hanging up.  Just for kicks, spray a little carb cleaner around the points 
 where the throttle shafts enter the carbs.....while the engine is 
running.....if  the rpm changes noticeably, the rebuilder may have not replaced the 
rubber seals  around the throttle shafts letting air into the carb changing 
the mixture at  random amounts depending on how the throttle shaft moves.
 
Chip Krout
Delaware Valley Triumphs, Ltd.
Skippack,  PA
1976 TR6 CF57822U

In a message dated 5/7/2012 3:41:24 P.M. Eastern Daylight Time,  
[email-masked] writes:

I have  inspected the linkage and don't find that it is hanging up
anywhere. Is it  possible though that it could be something with the way I
reinstalled the  linkage?