You can fix it if you try hard enough. You'll need the original OEM carb with all of its original parts in decent condition
. If you have put a carb kit in the original carb, take all of those parts back out and put all of the originals back in it. If you do not have all of the original parts anymore you'll have to re-acquire them.
You will need to read and follow the service manual recommendations
100% to set the carb up properly. If you don't you are wasting your time, so no sense in continuing...
Take the original rubber tipped float valve and stroke the rubber tip lengthwise (from the fattest section toward the sharp tip) using a stiff plastic bristle brush and hot soapy water. A stiff toothbrush type brush works for this. Rotate the float valve between your thumb and fingers a bit at a time as you work to brush around the entire diameter of the tip lengthwise several times. I usually spend about 3-5 minutes brushing them. When you get done the rubber tip surface will have become more coarse looking. All of the smooth and shiny appearance will be gone... and the tip surface will be much softer, almost fuzzy looking if you were viewing the tip with magnification. Rinse it with the brush and hot water, dry it and set it aside.
Next use a cotton Q-tip saturated with a polishing compound to clean up inside the brass float valve seat. You can use a rubbing compound intended for automotive clear coats, Brasso, Mothers polish, etc., anything that polishes brass to a brilliant luster. Don't use any aggressive abrasives... you want to polish the seat profile, not cut into it at this stage... Rotate the polishing tip either by hand for a few minutes, or you can chuck the Q-tip into a drill motor operated at a moderate speed. Keep the polishing tip wet with compound, replace with clean ones often and don't press too hard if you spin your polishing tip with a drill motor... keep it wet and don't get it hot. Clean it up well with carb cleaner once you get a smooth shiny surface buffed into it.
Remove and flush out the fuel tank and petcock. Assemble the original carb 100% per the service manual recommendations and let us know how it goes.