To answer your orignal question...
See the attached picture...
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The secondaries of your carb are controlled by a vacuum diaphragm.
That diaphragm is normally located on the passenger's side of the vehicle, an slightly to the rear of the centerline of the carb.
The top cover is about the size of a silver dollar.
The diaphragm pull on an actuator rod.
That rod pulls the secondary throttle shaft that opens the throttle blades.
To remove the actuator rod from the secondary throttle shaft, you must remove a 'C' clip.
That 'C' clip is very small, and easily damaged, so be careful.
Once the 'C' clip is removed, remove the actuator rod from the shaft linkage.
The rod can just hang in space until you decide to hook it back up again.
This secondary throttle shaft linkage MUST be secured to prevent the secondaries from opening.
Use a wire or 'zip' tie to keep them shut...
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Just out of sheer curiosity, Why the heck do you want to disable the secondaries for anyway?....
"I Have The Body Of A God... Buddha"