Depends on the age of the carbs - I can't see the jets clearly in that link. The springs you show are the throttle return springs as mentioned above. There is usually an additional 3rd spring operating directly on the throttle cable lever. Not aware of any return springs on the 'choke' other than the small springs I mentioned earlier, to hold the jets up tight when the choke cable is pushed home. You do realise that twin 'tiny' SUs like that are scarcely any better than a single SU of the same size fitted on a good inlet manifold with no water heating or 'hot spot' That's the only advantage the twins have (even the flow into the head is no better because it is disrupted by the cross tube ) - no heating of the mixture as it flows in to the head. And sadly - these pan cake filters are no good either - the face opposite the carb intake must be at least 1.5 X the diameter of the carb intake away from the carb. so for 1.25" carbs they need to be 1.5 X 1.25 = almost 2" deep.