FCR 39 CARB FLOODING

Friend and his son bought a old 250 EXC , I think around 05 model to fix up and play with , he says it ran when he bought it , with a fuel leak out the overflow , they then started cleaning it up , bought a carb kit and since then the carb just floods , Asked me to help , and I am now lost , Set the float level as per instruction to 7mm , did the airflow test and needle valve closes , but as soon as we refit and open the fuel tap , it floods , stumped , the seat is non removeable and if the cause , a new carb is the answer , but believe there is one person in PE that supplies and charge 19k .
suggestions please !