The newer carbs don't have slots for screwdrivers. They have some kind of ribs on the side of the adjustment screws and I have not been able to find a tool to fit them. The last one I had a problem with one or these I had to take a dremmel and cut slots for a screw driver.

For the featherlite, pull and clean the carb. You may have to use a small wire to clean out some of the passages. Compressed air is also a big help cleaning these carbs. In my experience, the gas tank caps do not go bad all that often.