I have just switched back to the original zenith carb from my 63 wagon after running a spare for the last few years. I re-built the original; repairing sloppy linkages and generally giving it a thorough going over. I gave it a first run this morning and found that it bogged down and stalled when taking off from the lights. Idle is set fast enough and idle mixture strength adjustment is as per the book (screw in and then back out until smooth running is just achieved).

One possible reason for the bogging down is that I may not have the acceleration pump linkage geometry quite right. Can anyone confirm that the acceleration pump should begin to activate immediately as the throttle mechanism moves off idle? As it is at the moment the throttle is part opened before the acceleration pump starts to travel. If anyone has a Zenith carb and could poke their head under the bonnet and work the throttle (with engine not running), I'd love to know if the acceleration pump moves as soon as the throttle moves from idle, or if there is some travel of the throttle before the pump starts to move. I am hoping that is the problem, otherwise I am at a loss to explain it.