The phenomenon of revving up briefly then dying, when it happens to a 2 stroke, nearly always means it is starving for fuel. You might begin by disconnecting the fuel hose where it attaches to the carburetor, and seeing how fast the fuel flows out of it when you turn on the tap. You may have a blocked filter in the tank.
If the fuel flows freely from the hose, you need to take a look at the entry port to the float bowl, and the needle and seat. You may have a partial blockage.
