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Tips
Tips

Fast idle

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AltaKnight

AltaKnight

Jedi Knight
Offline
My 1973 TR6 has the stock ZS carbs
I just can't get the idle speed down below 1000 rpm
I've tried about everything including cleaning and rebuilding them, centreing the throttle disks, cleaning and lubricating the linkages, balancing the airflow.
The only way to slow it down is by retarding the ignition which also reduces the power.
I'm wondering if the throttle return springs on the carbs are too weak since I can manualy force the throttles more closed and reduce rpm until the next time I touch the gas pedal.
All the linkages appear to function correctly.
Any brainwaves out there? /ubbthreads/images/graemlins/rolleyes.gif
 
Make sure your tach doesn't read fast. Mine reads fast by about 12% according to the inspection station computer and my old tach/dwell meter.
 
Make sure that your throtle linkage is not binding anywhere. Ceck the bushings on the bulkhead for the cross shaft. If these are worn or missing it will affect your throtle response. Did you check for any vacuum leaks around the base of the carbs and the carbs themselves?
If all of this checks out you may consider replacing the return springs since you can manipulate the throtle to get the idle down.
Best of luck! /ubbthreads/images/graemlins/hammer.gif
 
Tuck your foot under the gas pedal and lift...see if the RPMs go down. If so, then the linkage is binding. The accelerator cross-shaft is often bent when an engine is removed and replaced. I've seen this a few times. Another possibility is that you have worn throttle shafts. Try spraying some carb cleaner at the points where the throttle shafts enter the carb. If the RPMs go up, then you have a leak there. That kind of leak is at its highest influence at idle with high vaccuum. When you try to get a low tickover idle, the effect is so pronounced that the mixture ratio now won't support the idle, but the car will drive more or less OK throughout the rest of the RPM range.
 
My 250 idles at 1200 consistently, no matter what I do. Lower than that, and he putters out. The shop I take him to for serious work beyond my abilities indicated that I need a new manifold gasket, and that this was affecting air flow. I'll get around to it one of these days.

Where do most 6/250 people idle, out of curiousity?
 
Woops, that wasn't meant to be a SA remark, keystroke error.

That would be 1000 rpm, consistantly.

Bill
 
Mine idles at 900 RPM, rising to 1000 RPM as the heat builds under the hood.
 
[ QUOTE ]
Where do most 6/250 people idle, out of curiousity?

[/ QUOTE ] My fiance might say "on the couch in front of the TV".
 
Graham,
Please check you messages. I forwarded a cure for your problem.
 
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