dorothycd,
I've been struggling with this same issue on a 1996 HDS2135 Cub with 500 hours. On an earlier post where I had been running the tractor all winter, snow plowing - I had just put the mower-deck on and it wouldn't start at all. In that post, I mention a guy who found a small piece of plastic film had gotten in his gas tank and it would periodically block the fuel-outlet hole in the tank - starving the engine.
Well, I thought about it again and after having replaced everything except the fuel-pump, I decided to disconnect the fuel-line from the fuel-filter this past weekend - and guess what - No fuel came out even when I lowered the disconnected fuel-line to the floor. Blew some air through the line and there was some kind of blockage. Once freed up the fuel poured out of the line into my can. Reconnecting - my tractor started right up and ran.
When I looked inside the gas tank as much as could through the fill hole, I could see a tiny opening in bottom/back of the tank where the fuel line connects, but I couldn't see anything solid that would block the fuel-opening but the opening was really small compared to the 1/4 fuel line.
Not wanting to take any chances, I cleared the fuel-line once more, disconnected from the filter and siphoned all the old gas that was in the tank. Put in a fresh batch and it's been running ever since.
You might give that a try - doesn't cost a thing to see if gas is coming through the line.
Good luck,
Greynold99