Overheating, no coolant loss

[Kenny Dave]

Replace the float valve O rings as this is the most likely cause of flooding. Would be good practice to replace the main jet  O rings at the same time. No need to change the Main Jets or Float valves as the spurious ones are not as good as the original.
These are the sizes I used

Use Nitrile (Buna-N) SHA75 to 90       or        Viton® (FKM/FPM) SHA75 to 80
Nitril wokat lower temps and Viton at higher temp but wont make much  difference in Carbs. Nitrile is a bit cheaper
Sizes, I measured

Float needle valve: 7.5mm ID x 1.5mm cross section 
Main Jet: 5.5mm ID x 1.5mm cross section

Bought all mine here https://www.polymax.co.uk/o-rings/o-ring-selector/

Thanks unfazed, that's great info for the future. I've completely replaced the carbs now, so I'll see how they go. They look in much better condition than the one I've taken off, and I know they've been on a shelf in the garage for a decade at least. So I'll see how they go.