How do I get my 24A super colt to keep running?

My 24a sc runs for 3 seconds then dies and wont re-start. It used to run ok before I re- connected the tick-over arm ! Does this suggest its too rich or not rich enough?.Could anyone offer correct manner of re-setting carb.Its a Zenith and has only the primer button on top.
I saw an add with a Zenith carb and the chap ajusted the mixture and the air screw but mine hasnt an air screw.

Mike Ware
October 2011