Planes that have been sitting awhile most likely have oily gunk in the tank. Take the tank out and replace it, their CHEAP. New tanks come with a new stopper, witch you need. New fuel lines with a filter between the tank and mixture screw would be next.

Take the back cover off the engine and make sure it is clean and no gunk or rust. Open the mixture screw and blow out the carb to make sure it is not plugged up.

After you do these steps, report back your finding. Scoot