Pull the tank out of the plane and replace all of the fuel lines. I would say that 90% of carb problems are fuel tank/line problems. It only takes a pinhole in a fuel line to mess things up. Check after each "hard landing" also. I only use 2 line tanks so can't comment on that part of your problem. If you cant get fuel to easily come to the carb inlet, there is no sense in even trying to start the motor. Blow into the line that goes to exhaust and fuel should rush out of the line that goes to carb. If not, fix this before trying to start the motor.