Could be needle sticking or binding in the seat causing the fuel starvation. Or perhaps some trash over the seat in the upper chamber fuel inlet area? Like the other mechanic said and I agree...I've never heard of air in the line causing fuel starvation, or having to put suction on it to get fuel to the carburetor other than a fuel pump going out. It would run for a minute or so until the fuel in the bowl was used up, then quit. Would have to re-fill the bowl again by whatever means but if the pump was out it wouldn't run.