Vacuum Leak?

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06 Jun 2011 15:49 #455785 by BIGD
Vacuum Leak? was created by BIGD
My throttle will not return to idle very quick, and know this is a symptom of a possible vacuum leak among other things. I have replaced both intake and manifold rubber mounts, rebuilt and cleaned carbs well, checked but not replaced throttle cable. The 4 small rubber seals on my choke assembly are either damaged and 2 are completely torn, would this be enough to cause my idle and throttle response issues. If not other suggestions are welcome. Thanks Don

Had 1981 KZ1000 M1 From 1981-1995 Canadian Model
Have 1981 KZ1000 M1 US Model

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06 Jun 2011 16:12 #455787 by MFolks
Replied by MFolks on topic Vacuum Leak?
What kind of carbs? If the CV (constant velocity) the rubber diaphrams on top of the carbs may be torn. This is possibly due to the Alcohol/Gasoline mix being sold just about everywhere. It's attacking the rubber pieces of the bike fuel systems.

1982 GPZ1100 B2
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)

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06 Jun 2011 16:12 #455788 by Patton
Replied by Patton on topic Vacuum Leak?

BIGD wrote: My throttle will not return to idle very quick, and know this is a symptom of a possible vacuum leak among other things. I have replaced both intake and manifold rubber mounts, rebuilt and cleaned carbs well, checked but not replaced throttle cable. The 4 small rubber seals on my choke assembly are either damaged and 2 are completely torn, would this be enough to cause my idle and throttle response issues. If not other suggestions are welcome. Thanks Don


If not already done, would that the automatic timing advancer is functioning properly, and isn't sticking or binding due to rust or corrosion or whatever.

The advancer unit may require lubing or both cleaning and lubing.

Viewed under a strobe timing light, the advancer should quickly move back and forth as rpm is varied by blipping the throttle.

It might be that rust/crud/gunge is preventing the advancer from immediately and fully closing as it's supposed to do when the carb throttle slides are closed.

Good Fortune! :)

1973 Z1
KZ900 LTD

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06 Jun 2011 16:31 #455792 by BIGD
Replied by BIGD on topic Vacuum Leak?
BS34 and the rubber diaphram's seem to be fine.

Had 1981 KZ1000 M1 From 1981-1995 Canadian Model
Have 1981 KZ1000 M1 US Model

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06 Jun 2011 16:32 #455793 by BIGD
Replied by BIGD on topic Vacuum Leak?
Timing advancer is clean and lubed.

Had 1981 KZ1000 M1 From 1981-1995 Canadian Model
Have 1981 KZ1000 M1 US Model

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06 Jun 2011 18:45 - 06 Jun 2011 18:46 #455825 by Patton
Replied by Patton on topic Vacuum Leak?

BIGD wrote: My throttle will not return to idle very quick, and know this is a symptom of a possible vacuum leak among other things. I have replaced both intake and manifold rubber mounts, rebuilt and cleaned carbs well, checked but not replaced throttle cable. The 4 small rubber seals on my choke assembly are either damaged and 2 are completely torn, would this be enough to cause my idle and throttle response issues. If not other suggestions are welcome. Thanks Don


:unsure: Are all the o'rings on pilot air screws in good condition?

The 4 small rubber seals on my choke assembly are either damaged and 2 are completely torn, would this be enough to cause my idle and throttle response issues --- Would test for air leak in the usual manner, by spraying WD40 or carb cleaner in the areas leading to the seals, while engine is running at idle rpm, and watch for noticeable change in rpm or smoke from the exhaust, which would indicate that the spray is being ingested.

Good Fortune! :)

1973 Z1
KZ900 LTD
Last edit: 06 Jun 2011 18:46 by Patton.

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06 Jun 2011 22:01 #455847 by BIGD
Replied by BIGD on topic Vacuum Leak?
O-Rings are brand new. Thanks

Had 1981 KZ1000 M1 From 1981-1995 Canadian Model
Have 1981 KZ1000 M1 US Model

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