I think you are getting foreign material in the needle & seat. Put a in line filter in the fuel line. Make sure the filter in the carb inlet is good & has a spring behind it to keep it up against the inlet fitting. These reman carbs are usually not right. You may have to pull the top off & check the float & float level. Make sure the power valve piston is working. I'm assuming you have the model B carb used up to 68. After that it will have a Monojet which is not quite as simple.