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If it were me, I'd disconnect the feed line to the fuel pump, then take a peice of rubber hose from that feed inlet and drop it in a gas can (your lawnmower's can for instance) so the fuel pump isnt' drawing the 15 year old fuel through the lines. If it starts, then you keep moving on as far as cleaning out the fuel line from the tank to the pump. Other than that, give it a try, and fire that puppy up!
Before I started mine, I disconnected the fuel lines at the fuel pump and let them drain to get all that old gas out. Then hooked them back up and put new gas and some fuel system cleaner in the tank.
As for my radiator, yes it is shot. it has a leak where the upper radiator hose connects. It's a very small leak though. Only leaks a few drops each time I drive it. I haven't had to add any to the overflow tank yet. It's not bad enough for me to replace now. I'm hoping that it will make it until winter. Then it will get a new one.