Thanks for your reply.
I don't believe there is any link in the fuel line otherwise we would have noticed the fuel hanging around.
It is a 2-stroke 49cc bike. I shall spray the carb with WD40 and see what happens.
My son's mini motorbike is a 49cc one.
After riding for a few minutes, it starts to cough a bit and then cuts off. After a few minutes, it starts again and then cuts off a few minutes. We had never managed to ride it until the fuel run out. I fitted a new air filter which did not make...