These symptoms mean its running weak,so there isnt the right mixture of fuel and air going into the combustion chamber it has too much air and not enough fuel.The problem will be one of the following
1,carburettor jets blocked or leaking float(ie full of fuel not air)
2, a crimped twisted or blocked fuel hose or air pipe to the vaccum operated fuel pump or carb
3,A faulty vaccum tap or fuel pump
4,water in the fuel making the mix weak
5,not enough fuel in the tank!
6,incorrect fuel or mixture of diesel or similar fuel with the petrol
7,blocked fuel filter they have one in the tank but i dont think there is an inline one.
8,split air hose on the air filter or not fitted correctly maybe the hose has come off the back of the carb or the airbox lid is loose.
these are the most likeley problems but there will be more options to check these carbs run a carb with an accelerator pump on them so when you open the throttle up it pushes a plunger down into a small well in the float bowl and it forces a pulse of petrol up through a jet into the venturi of the carb to give it the extra fuel it needs to compensate for the large amount of air it gets if people just open the throttle up quickly.so if you can get to see the side of the carb check when you open the throttle to see if the plunger on the side with the small rubber gaitor around it pushes downward and the returns upwards when the throttle is released before you check any of the above.ok good luck
adam bike doctor, January 2010