I’ve been chasing a terribly poor idle and focusing on my Zenith 10920 carb to be the cause. Now I just completely rebuilt the carb again with a new kit from carbking. This time I bought the 2 Zenith check valve removal and installation tools so I could replace them as well. With the carb completely disassembled including the checks and ball, I soaked the works in a gallon carb cleaner for 3 days before rinsing, running a thin wire through every passage then thoroughly blowing out everything with compressed air. Then I soaked again for 24 hours and repeated. This carb is now cleaner than a new baby bottle with new parts installed with the proper tools.

Meanwhile each time I’ve cleaned the carb I fall back 2 steps or more.

I think I’ve been chasing a red herring. I’ve gone from a terrible idle to nothing. Don’t want to run at all. It tries to start but sounds like what you might expect if the spark plug wires were out of order (they are not!)

Now to the point, with distributor cap off I can rotate the rotor a few degrees CW by hand and feel spring tension. When I let go it moves back CCW to a stop. However I can then turn it slightly more CCW and it stops there. With a slight turn back CW to the initial stop it will stay there but I can hear a click when moving it there.

Is there a bonafide expert reading this who can tell me this is abnormal, or can someone do me the immense favor of removing you distributor cap to check and see if it does this same thing?

Many thanks to all who may help me!!

Mike Barnes
1950 GMC 1-ton pickup