We are talking about the choke butterflies , not the throttle butterflies .... Yes?
You imply that the lower and middle carb choke butterflies are operating correctly. That is normally fully open and fully closed when the key is pressed in to activate the solenoid .....Yes ?
The top one however is not operating correctly.
Slacken the screw which clamps the operating arm to the shaft. (See the snip the from your photo below.) Position the butterfly correctly and then tighten the clamp screw.
If necessary adjust the bottom one in the same way .so that all three operate in the same way.
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Looking at the middle carb are you sure this spring is positioned correctly ?
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I am not sure but I think the throttles should open partially when the choke is operated. Can someone confirm this . If I am right do they?
Make sure that all three throttle butterflies operate together from closed to fully open