Hows the idle quality when it does idle? Do you need to blip the thottle now and then to keep it running? Make sure the idle is 1400 give or take 100.Air filter clean and oiled?
You may be on the lean side, in the pilot circuit, try adjusting the fuel mixture screw, out,about 1/4 turn, to richen up the idle.

 

Same used to happen to me i just made it rev louder buy the rev screw on the side, and it works
tom