Sounds like you have some crud in your tank that gets moved around a lot while you have a lot of gas and plugs up your fuel line when the gas gets low. You should have a micro screen in the connector for your fuel line fron the tank. The screen is most likely the problem but the only way to find out for sure is to pul your tank, dump it out and remove the valve. Once you do that you may want to get some alcohol and swish about 1/4 of the bottle around in your tank. Once that's done repeat a couple more times to make sure you got all the crud out. Use the last of the alcohol to flush out the valve and the screen.
This should do the trick. If you want to avoid the crappy gas try to go to newer gas stations or stations with newer storage tanks. If you see a fuel truck filling the tanks at a gas station don't get gas there for at least an hour after the truck leaves. When they pump in new gas all the crud in the bottom of the tank gets stirred up; some of that ends up in cars and bikes.
Also check your fuel lines for damage and make sure they aren't collapsing. If you are in an area that uses E85 ethanol you'll have to try to avoid those stations. E85 can mess up fuel lines and fuel pumps on vehicles that are not flex fuel ready.
Retired USAF, IYAAYAS!
2008 V-Star 1100 Custom Bobber project
2011 Crimson XR with Forged Highway Bars / Hard Bags / Passenger Backrest, Ness parts including Smooth Layback Plate Frame/Mount / Rad 3 Mirror / deep cut grips / drivers floorboards /shifter peg / brake peg / passenger pegs. Witchdoctor black rack, Lloydz filter / timing wheel / VFC III, 7Jurock windshield, Drag Specialties seat.