Usual suspects:
Inline fuel filter - replace (even if it looks fine, water can make paper filters swell up).
Gas cap - unvented cap on an unvented tank. Vacuum builds up and overcomes the fuel pump.
Fuel pump - said you changed it.
Little filter screen in the inlet fitting of the carb - some carbs have them and most people don't know they are there.
Sticking float valve - sticks in the closed position (especially true with soft seats. Replace.
Debris in the float bowl - happens if no filters between tank and carb.
Debris in the tank - large pieces blocking outlet.
And don't forget vapor lock - but this is winter.
By the time you get to the end of the list it should be running.
