Bottom pour spout clogged

With the lead molten in the pot and wearing a leather glove and safety glasses. Hold a small straightened paper clip with a pliers 
and try to clear the debris from the spout. Have the valve in the open position when you do this. There are probably oxides of lead and other metals blocking the spout. You should be able to clear them using this method. It may take a couple of tries. When you get it cleared out make sure to flux and stir your lead often to remove any other debris that may be in the alloy.