Bike dies when choke is on

A couple months ago I assembled a set of 37 year old carbs for an 81 Yamaha XJ550 Seca that had never been used and put them on the bike. It took care of a hanging idle but now my bike shuts off if I apply the choke. If I barely apply the choke it will rev slightly higher but if I put if full on the bike will die. With the original carbs (which I wish I never took apart in the first place) when I applied the choke on a hot engine it would just rev very high. Now is just shuts off when I apply full choke. The plugs are black and sooty which means I'm running very rich. The bike often sputters and dies after I stop at a stop light and then take off. There's a lot of popping coming out of the exhaust and a little more rattling around in the engine then there use to be. From what I've read it seems very possible that the needle jets from the choke are not sealing properly when closed so I'm constantly getting an overly rich mixture. Besides bench synching I haven't fine tuned the carbs and I feel like when I turn the mixture screws that it doesn't do a dam thing. Does anybody else have any ideas how to fix this?

 

If the bike is running and you then apply the "choke" (this really a fuel enrichment circuit) you are putting extra fuel so yes it will foul the plugs and cause them to be black and sooty . Can you take the bike for a high speed run and take a plug chop and pull plug see what color tip is . Set all 4 carb mixture screws at 2.5 turns out is best setting ....if you have a colortune plug you can dial in much better. Or you will have to do the plug chop method , please note your mixture screws can be set different to bring cylinders into range . Have you done a running synch will need either a 4 vacuum gauge manifold or a 2 bottle mamomter ,or better yet morgan synch gauge .

 

Eh? Why are you applying the 'choke' if it does this - leave it for start-up only as intended.