Thanks for the responses everyone, but it's not really the screw that is the issue, but like Andy says, this part number also has the springs which is what really seems to be the issue. Spending the money on a second set of carbs seems a little overkill for a couple of springs. I guess I can try and source some other springs from something else, but I was just trying to fit the OEM stuff. If someone has any MC21 air screw springs they want to part with, PM me!