What kind of ignition does it have? If it uses a points and condensor, sometimes condensors will heat up after awhile and fail. Then when they are cool work for short intervals. I'm guessing it's electronic ignition though, so then maybe some sediment in carb or fuel filter that plugs it , though you did say it squirted gas fine when you pumped the petal. How is the coil wires? Are they old and cracked? They can drive you nuts too. It has to be something simple. Next time it stalls, give it a squirt of starter fluid. If it lights up right away, it probably is a fuel supply problem, if not start checking electrical and see if you've got a spark at the plugs. Hope this is helpful. Steve.