While fitting new carb balancing screws, well that's what I think they are, 1 of the little beggars is just spinning and not tightening. Thread is good on screw , described as 5 x 6mm pan screw. I'm tempted to blank it off but would negate balancing carbs or that one later! Any ideas I'm thinking another helicoil required 😒 Photos attached to show location.