Do you mean that they are seized and you can't turn them?
If so, the first thing I would do is to apply some penetrating oil and let them stand overnight.
Make sure that your screwdriver is a very good fit in the slot.
Try tapping the end of the screwdriver as you turn; try clockwise and anti clockwise.
If you attach a Mole (self locking) wrench to the driver this will give some additional leverage if required.
When attempting to turn apply a gentle turning force that you build up.
If all goes well you will have loosened the screws. If it hasn't you will have Donald Ducked the screw head.
Wow! So they are all tight down into the seat? You have your work cut out for you. Bad enough when you have one stuck, let alone all four. Work slowly and try not to strip them out, lots of penetrant will be your friend. But you may have a tough row to hoe ahead of you.
Left-hand drill set, probably gonna have the screw turn itself out as the bit catches.
The tip which was sticking-out the sidewall of the venturi, I used a deep socket, something like a 5/8", and I carefully placed it over the protruding brass tip, and I used it to push-into the female-threaded passageway the broken-off tip. It fell-out the end, below the CV cap. I used a tap to chase the threads, careful not-to go too-far into the passageway, I used a blind-hole tap. I measured an unmolested air bleed screw hole's depth to-where it steps-down, and used that measurement for chasing the threads.
Use an 8mm/1/4" drill bit to get a good center, or a centering bit of that size, even better . Then drill the head for, easy out, extraction. I tap the easy out in then put the easy out in a vise and twist the cab body. Usually the tip can be dislodged by tapping on the carb body. +1 to pushing the tip from the inside, if needed. Anyone that cranks the needles in like that?
im still working on it and i'm getting close. but just in case i pulled another body and started cleaning and noticed someone had drilled all four of these caps removed them done some sort of surgery and replaced them. then they put screws in the caps. does anybody know what for?
The only thing i can think is to drill the seats for more flow.
The red circle looks like it’s covering the cap the allows you access to change the needle valve seat In the float chamber. Some people remove these caps by inserting a screw on top to pull them out, but no need to do that as you can push the needle valve seat out from the inside using a socket and clamp, the cap easily pushes out with the seat. That cap only has an ‘o’ ring holding it in. There are posts already on this site giving instructions on this procedure if you need it, certainly helped me do the job. But the caps with screws inserted means someone has probably changed the needle valve seats the long way.