Here's some possibilitys for you.
#1 is the pipe puttin out pressure? When you turn over the motor, it forces the air out the exhaust, which forces air into the tube that connects to you tank, pressurizing it.
Make sure your pipe outlet (the place where thos fuel hose goes) is not plugged, or full of gas/oil
#2 Fuel Tank is it full? half empty? How long has the gas been in the tank? A half empty tank wont provide as muc pressure as full one.
#3 take off the hose from the pipe, blow into it(the hose). You should see the fuel leave the tank, and fill up the line to the carb. does that work to get gas to the carb?
#4 old fuel If you left fuel in the tank, it is possible that fuel is etting to the motor, it's just old and will not burn.
If you left old gas in the tank, drain it. Take the hose off the carb point it at the ground. Tak the hose off the pipe, and blow into it. That shouldpush your old gas out the line. Making room for the new stuff.
#5 Is it possible you have an air leak in anyof your hoses? Is it possible your tank has a hairline crack, and won;t hold pressure?
#6 It is possible your needles are plugged. Remove them both. Blow air through the fuel line.make sure they are clean and debris free. Set them back tofactory defaults.
Good luck, let us know what's up.