 Thats weird
Behind the timing case cover attached to the front of the cam is a circular piece that is mounted offset from the center line of the cam.. It's called the fuel pump esentric. It hits the lever on your fuel pump as the cam spins thus giving the carb fuel. Not sure if it's broke or loose but i might wanna verify that if i were you. Instead of removing fan, waterpump, and timing case cover if you take of the fuel pump and rotate the motor you should see the esentric. Again not sure if that's the issue but it might be worth lookin at plus if it aint it, it's a good excuse to drink beer. ha good luck | 
