I spent hours last year to stop the carburettor running very rich, Its a very very poor design of how the float works bit like standing on one side of a Coracle as little weight upsets it so same with the float gives little weight to lift needle to stop flooding, so added set screws to opposite side helped a bit but still very poor, been like it all its life as piston and rings very worn out but rest of machine shows little use, so after repairing tin work and freeing off all the cylinder parts I decided to have another go at the carb and lowered the fuel level a bit more and put bit of solder on the slide to reduce the Venturi effect has sorted the issues. Its idled today for two hours and plug is just brown, I couldn’t run it more than half on hour before plug sooted before.