1982 XJ550 Seca Carb Kit - advice

Hi Folks
I am rebuilding the carbs on a 1982 XJ 550 Seca. I got these carb kits from K&L and I can't figure out what one of the parts is. It's a small metal (aluminum?) disc, appx 6.5mm diameter, 3.5mm thickness, and a small hole (<1mm) in the middle. I can't find it in the carb diagrams, I don't see it in any tutorials online, I have no idea what this part is. I carefully took apart the original carbs and can't find this part there, either. What am I supposed to do with it?

 

that disc is the plug cover for the air mixture screws in the carb. it was a factory only set thing and then caped so owner could not adjust it.
funny I picked up one off the floor today
goes in hole over the screw to left of plunger in photo

 

It does indeed go in there! Thank you. Also explains why I couldn't find any when I was taking everything apart. I wish whoever worked on this carb before had left them in place, rather than taking them out and stripping two of the mixture screws... I was able to get one out with a screwdriver and a rubber band, but still have one stuck. I am planning on trying to get it out with a screw extractor bit. Wish me luck.

Actually, nature had supplied an alternate version of these plugs. Some kind of insect had laid a bunch of eggs in the cylinder on top of the mixture screws in two of the carbs. It looked like it was just full of dust/dirt/sand, but when I cleaned it out a few very dried and dead worm-like things came out of there. I suspect this bike had been sitting for a while...

 

easy outs work just soak the screw a couple of days with renetrating oil

#1 easy out is size just be carful drilling