Woah! This rings a bell......
I've never had to swtich carbs, all my Series always came w/ Webers on 'em, but.....
I do recall something about, when a Weber is put on replacing a certain carb, you have to change the way the arm pulls....
I can't say if it was where a Solex or the Zenith was being replaced, but I would say, if you can get someone else to step on the pedal, see where the lever is, then as they left off, which way it moves, you will want to disconnect the linkage, rotate the springed-lever to the other direction, so it will function the other way....
(Did that make sense?)
-L
'72 SIII SW 88"
'60 SII 88" RHD