Randakk's kit includes the o-rings & washers for the idle screws but not the screws themselves.
Bikes made for the US market came with caps glued over the ends of the idle screws that had tabs that kept the screws from being turned very far from the way the way the factory set them (the rest of the world got unaltered screws). For most models it meant that you had to remove the float bowl to unscrew them but I seem to remember reading about some that you had to cut the tab off to properly clean the carbs. I seem to remember reading instructions for gluing the caps onto replacement screws in a manual somewhere (can't remember which bike) but I can't imagine anyone actually doing that.
Those screws look like the original ends with the caps have been broken off, although I would think that anyone who did that would cut the slots so they could adjust them.
BTW: I like to soak the brass parts of the carbs in methyl hydrate (AKA methanol) to soften any varnish. If you don't have access to an ultrasonic cleaner, Randakk recommends boiling them
Old School Carb Cleaning Methods | Randakk's Blog
If you can find a compressor accessory kit like the one shown below, screw the "needle" (normally used for inflating balls &c) directly into the gun body where the nozzle normally goes and set the compressor's regulator to 10-15 PSI and you have the ideal tool for blowing out the passages inside the carb.