Binding Secondary Throttle Valve

[Laldog]

For reasons that escape me, the secondary throttle valve on one of my Weber carbs is binding up, creating a very unique driving experience.

This condition repeats itself independently of the linkage, (disconnected from the linkage, it still binds up)
I shortened up the return spring a bit to increase the tension, no change.
I sprayed the sh*t out of it with carb cleaner, no change.

Any ideas of what may be the cause?

Winter is coming so I'll be putting the car away in a little bit, but I think spending the winter tearing the carburetor apart can only lead to bad things.

Any and all suggestions are entirely welcome.

 

[Stevehose]

usually there is a screw that is supposed to just barely keep the secondary throttle plate open and from binding shut, it's open just enough to allow a very small amount of air to pass at idle, measurable by a synchronmeter and DGAV adapter. If it's not that you may have some worn secondary linkage that is grinding together.