My US41 does not want to run. It will start if you prime it with a little fuel down the carburetor but only runs long enough to burn off the prime (a few seconds). After opening up both needles, it will run but is not very responsive to needle adjustments. I think I have a fuel draw problem. I cleaned out the screen in the carb but this didn't help. The pump is sucking fuel. We hooked it up to my gallon gas can thinking the tank might have been clogged but it didn't help. Any suggestions?