sounds like you are losing your fuel prime. *next thing i would do is replace the primer bulb. *they do go bad after a while(cracks, etc.) *that is a common problem(most often times overlooked). *if that doesnt do it then check fuel filter, and water separator if you have one. *if the engine runs fine except when idling then more than likely it is in the fuel delivery. also, make sure all fittings and clamps in the fuel line are tight.
hope this helps.

C.