Sounds to me like there's dirt, varnish, particulate matter, water in your carburator circuits/jets. You'll have to completely remove and disassemble the carb, remember to remove the high and low needles too. Blast the carb & parts out with a can of carb cleaner. Then blast it out with compressed air. You may need to repeat this a few times. Also, look at your fuel pump diaphragm. Does it look stretched or blistered out? If so, that will need replacment. Take a look at your inlet needle. Does the viton tip look like it have a ring wore into it? Does body of the inlet needle have light scratches, wear marks, or shiny spots? If so, that will need replacement as well. Now look at the inlet needle pivot rod and lever. If there are wear spots present those will need replacement too. After all the parts are cleaned, worn parts replaced, begin reassembly. Let start with the fuel pump side. Dip the fuel pump diaphragm into some fresh clean mix gas, and align/place on to the fuel pump side of the carb. Now dip the fuel pump gasket in mix gas, align/place on top of the pump diaphragm. Now align/place the cover on to the carb over the gasket & diaphragm. Tighten the screw securely. Now the metering side of the carb. Take the inlet needle and dip the tip in some mix gas, and place the inlet needle in to it's bore. Now the tricky part...Place the pivot rod into the lever, hook the lever into the inlet needle head. With a tweezers or similar instrument, place the spring under the inlet needle lever assembly. Use a finger/thumb to hold the assembly down. Place and tighten the pivot rod screw securely with you other hand. With a straight check to make sure the end of the inlet needle lever is level with the deck of the carb. You will need a small screw driver or two to make adjustments either prying up on the lever if lever is too low, or pressing down on the lever if it is too high. Okay, now dip the gasket in mix gas, and align/place on to the carb deck. Dip the diaphragm in mix gas, shake the excess mix gas off. Now align the diaphragm and place over the gasket. Place the metering cover over the diaphragm & gasket and secure with 4 screws. Now srcew in your high and low needles in to their proper positions. Screw in the needle lightly into their seats and back off 1 to 1 1/4 turns. This is the basic setting to make adjustment off of. If you have access to a pressure/vacuum tester make sure the newly assembled carb hold +0.8 BAR, and -0.4 BAR 30 seconds.
Hope this helps.
Nick G.