Re: Not an antique, but I need some help.

[Don]

OK, you had the jet out, and had no trouble doing it. I’m sure you did no damage provided your screwdriver was not scraping on the internal threads of the bowl. Be sure the jet is completely reinstalled and snug though, it can walk back out slightly and create a lean high speed condition if left loose.
I don’t think the lead shot comes with the carb kit, did you buy one separately? In any event, it looks like the lead shot goes right near the core plug, but you can not trust those diagrams and I don’t have a carb handy to look at. Did you remove the original lead shot? If not, and the lead shot fits loosely in the passage, you are placing it in the wrong spot. Some of those open holes in the carb body are vents, and meant to be open.
Now back to the carb synchronization. Let’s start with the choke linkage. The choke is linked to the carb butterfly so the butterfly will be cracked open when the choke is engaged. So, if that linkage is messed up, the butterfly will be cracked open when the choke is off. You could simply remove the link between the choke and butterfly to eliminate this possibility for now.
Next, have a look at the carb throttle roller up by the throttle cam. The cam should NOT be touching the roller at idle speeds (when the throttle is retarded below the two little marks on the cam). The throttle will be held open slightly if the cam is holding the roller open at idle speeds and the engine won’t idle. Finally, just because the cam is not touching the roller does not ensure the throttle plate is closed, which is why I wanted you to look at the throttle plate with the carb off to ensure it is closing and not binding. You could always temporarily remove the link between the butterfly and cam if you suspect something is binding in the linkage between the butterfly and cam.
You will find a long thin horizontal link between the throttle roller and mag plate linkage, this is the economizer linkage. If someone has grossly misadjusted this, it may be holding the butterfly open at idle speeds. You will see a little brass clamp with a set screw on the rod. Don’t mess with it unless it is misadjusted holding the throttle open, simply loosen the screw and move the clamp back towards the rear of the engine. Again, don’t mess with it if this is not an issue.
Finally, back to something I should have began with when talking about ignition problems, the spark plugs! Again, ignition problems can disguise themselves and sound like fuel problems. You might want to try a new pair of QL77JC4 plugs, even if the ones you have are new already, just cuz the plugs are new doesn’t mean they are any good.