Does anyone have an explanation (and cure!) for petrol leaking from the throttle stop screw on a monobloc?
Check the float level. I think the fuel level should be below the top of that thread.
Float may be sunk, stuck, or pinched by a new cover or gasket. Dirt may be holding the float needle open.
I'd agree with limeyrob. It sounds like a float issue.
Let us know how you get on. 🫡
Operator error! I had leaks at more or less every fibre washer, and as I dealt with these I would tickle the carb to 'test' the repairs. Eventually they were all fixed - but so was the habit of 'tickling the carb to test'. I eventually engaged brain (with the help of limeyrob's input and a manometer tube on the pilot jet) and realised that holding the float down to flood the carb (i.e. tickling) was causing the fuel level to rise above normal and come through the only unsealed orofice. Sure enough - if I allowed the bowl to fill normally, I got the correct fuel level and no leak.
So the cure was to stop tickling it!
I guess I have never, when tickling my other monobloc equipped bike (A50) as part of a cold start, run round to the other side of the bike to observe fuel coming out of the throttle stop fuel.... But why would you!