good luck!!! Remove the carb from the motor. Remove all removable parts and clean & air blast. On the left side of carb you will find two round black plugs which have a serated edge for a special tool to adjust the air screws.(I did not have a special tool for this) Use a dremel tool with a thin cutoff wheel to saw a slot in the screw heads deep enough for a small screwdriver. You will have to saw through the aluminum housing a little to do this. Remove the screws. (Best to count the number of turns to close off) Make sure you count the number of turns that it takes to remove the screws as you will start there to adjust the carb after you air blast the holes that the plugs are in. Clean, reassemble & adjust the screws you sawed the slots in. I was ready to throw my 2 year old trimmer out and I gave this a try. Worked for me.
3.2 ounces per gallon
The mixture is a 40:1 ratio, that's 3.2 oz of two cycle oil to 1 gallon of gas
The idle speed of the carburetor on a featherlite fl20 weedeater can be adjusted by turning the small screw that is located right next to the choke setting switch. For the best adjustment, the featherlite should be on and running. If the weedeater is running rough, the mixture can be adjusted with the low and high (labeled L and H) mixture tamper proof screws.
Weedeater products, or FeatherLite Weedeaters are made by Poulan. The web address in weedeater.com. There you will be able to put in the model number (ex. FL20), and select type 1. You will get an illustrated parts list and order any part you need.
Try this site for a free manual download: managemylife.com
According to weedeater.com they are all to be .25..