[sam's 72]

When you pulled the filter, you said the fuel look funky, then you drained the tank, and started over new again, only to find out you got the same problem. I would start back at the tank again, get it as clean as you can, gas turns to varnish after a long period of time then when you put new gas in, you get these small partical look dibre floating around, I would clean the tank the best you can, then get air, disconnect the fuel line at the carb, and at the tank and blow it out with compressed air, once this is done, then go into the carb, and check what ebfabman said, since you started it back up, I would check the filter again. I had this same problem one time with a boat. friend of mine bought a boat that sat for a year or so and this is what we did to get it running, it would be easy if you could get the tank out, but that is a job in itself.
Good luck
Sam