A vacuum leak is the first thing I thought of also. The line from the dist. to the carb would not cause that problem though. That is ported vacuum & only a small amount can go through it. First check your accel. pump. After you shut off the engine look down the carb throat & work the throttle from a closed position. Each time you move it a squirt of gas should go into the carb. throat. If not you have a problem with the pump in the carb. Check the link that goes in the lever to the pump rod. It can fall off. That carb is basic & simple to work on as carbs. go. They work good when right. It is easy to take the top off & check the float level & power valve. You may be getting some water in it.