sounds like u do need to have it cleaned....sometimes running it dry is the worst for an engine because then there is just a tiny amount of fuel in the lines and that can cause the varnish to develope...i would suggest leaving a full tank with extra strong stabil in it, and then running it for a little bit to get the stabil circulated.

did you play with your adjustment screws? i cant really tell you how to fix them if u did...but ur manual may have the factory setting for them.

good luck

If your machine has a Tecumseh engine on it--here's the fix.
Shut off the fuel valve, if it has one on the fuel hose. If the carburetor has a round fuel bowl on it, with a brass hex head bolt holding it on--remove the bolt, and the gas will run out some. hold that bolt up so you can peer at it. Check in the threads, or just above them. There is usually a teeny hole no bigger than a stripped wire tie from a loaf of bread wrapper. Poke the wrapper tie into that teeny hole, then make sure any other holes are clear, blow thru the end of the bolt, put everything back together, turn on the gas valve, and try it. Also, check the breather hole in the gas cap, for a mud wasp egg in the hole. They like to lay an egg in there, which plugs up the hole, and gas will not run down into the carb bowl! The wasps do this in the summer when you aren't using the machine.
NOTE: You should install a fuel shut-off valve if there isn't one on it. Cost is around $5.