Needle jet tube has very tiny holes I have seen three in tube one be just above thread area and one are two more up tube take small wire out of wire brush this may small as need clear holes.

Here is a link that might be useful: Needle jet

This post was edited by gator_rider2 on Fri, Sep 26, 14 at 0:45

I surmise your carb isn't getting enough fuel to it.
Probably because of-
1. Vent plugged in gas cap.
2. Fuel line deteriorated internally or blockage in the tank.

Visualize an insufficient "trickle" of fuel going to the carb.
While the engine sits, the carb bowl slowly fills.
You start it and the engine is using fuel just slightly faster than it flows to the carb.
The fuel level in the bowl slowly decreases until it starves out.
Let the engine sit and the scenario repaeats.

I'd also surmise, that it quits sooner if you are loading the engine down by actual mowing vs just letting it run?

Thanks guys will check it out.