Thank you. I appreciate the advise. My idle circuit has 2 jets in it. A #50 on top and a longer #15 below it. This is a VM22ss carb. Sorry, if I am not using the correct terminology of pilot jet / slow jet / idle jet. My 1978 KZ650B won't get a nice lopping idle unless I have the carb lever pulled. If carb is pulled halfway, I can adjust the thumb idle center screw from 4rpm down to 2, but she struggles below 1500rpm. If I close off the choke lever, it dies flat off. It will die off flat even at 3k rpm. Won't restart unless the choke is on full or half On.
My fuel/air mix screw that inserts below the bowls is at 1 1/4 turns out. I tried various fuel/air mix numbers. 1/2 turns out....sort of same. 1 1/2.....sort of same. 2 1/4 .....sort of same story. Engine temps reach 220 degrees on all 4 cyl. Float levels are at 23mm.
With the choke lever 1/4 to 1/2 ON, I can repeatedly run the bike for 5-10 minutes. Usually at 2k rpm. I plug the tank's vacuum tube on cyl2 and use a bottle to feed the fuel. Standard airbox in use. Main jet 90. Carbs cleaned several times. Not the choke plungers though. That will be my next step. New jets and fuel seats in use from a generic carb kit.
Intake boots are new and tight. Air box boots also new and sealed well. I haven't tried taking out the K&N air filter in the standard box. I might try that. I do one change at a time.
My thinking is the #15 jet needs to be larger from spec, to not need the choke to be on. Kits I see are all #15s though. Maybe something is plugged in the plunger choke area.causing this behavior. Thanks for your advice.