Weber air leak?

[JHE007]

I have a problem(s) with the Webers on my +2, there are two symptoms which may have a common cause. The symptoms are that the engine will not idle below 1300 rpm and that one of the idle mixture screws has no impact on idle speed (the other 3 are fine). The one idle mixture screw was feeding the first cylinder. Unsuccessful attempts to isolate/fix the problems so far are:
Serviced both Webers, replacing all gaskets
New o?rings and thackerys for the connection to the inlet manifold
Blanking off the vacuum take-offs for headlamps and brake servo.
Swapping over the position of the Webers. Same idle mixture screw still having no effect on idle.
From reading the other posts I think this points to an air leak somewhere in the carb. The fact that swapping the Webers over had no impact would suggest to me the leak is not around the o?rings. When servicing the suspect carb the butterfly valve seemed to seal as well as any of the others. Looking down the inspection hole showed it in same position as the other valve at idle. So my question is how to trace the leak (if it is one), and could it be anything else?
Any suggestions would be much appreciated.
Regards
John

[quaybook]

Hi John

Do the carbs balance ok? Mine wouldn't and it turned out to be a twisted butterfly shaft. I'd inspected it visually through the progression drilling access and also by shining a light through the choke and I couldn't see a problem, but that is what it was. My only other thought is the startup enrichment device - if the plunger on that choke is not sealing properly.

Vernon

[prezoom]

Difficult, but check the leather seals on the throttle shafts. Mine were completely dead, dried out and had shrunk away from the shafts. Installed new ones with new caps, but before, saturated the seals with with leather conditioner.

Rob Walker
26-4889

[DeanG]

Spraying carb cleaner around the can help show leaks. If the rpm changes after a shot of carb cleaner it is a good indication that you have found air leak. The 2 previous posts are in line with my experience. Good luck.