Ok people need some info i have a beta evo 300 did some work on the head before Christmas all is fine,yesterday fuelled it up it ran for all of 5 minutes then died fuel coming from the little nipple bottom of carb asked a mate to have a look he stripped it down and found the exhaust had about 3 carbs worth of fuel in it any suggestions what the cause could be thanks

Fuel is leaking past your float needle and seat valve uncontrolled.  Could be dirt, could be worn parts and it is a very common problem.  Same happened to a friends Beta evo here just last week, he shut off the fuel and gave his carb a bump and the float corrected itself at least until he got home.