Kitgage, how did you make out with the FS80. Rebuild kits are out there. TK carb with the round fuel pump. If you got it running and the overflow constantly pours fuel out, here is a fix. I have an old FS80 as well. Just drill a hole in top of fuel tank and run a line from overflow back into tank. Make hole a little smaller so fuel line fits tight.If you don't have air filter and housing and don't want to pay the high price for an NOS stihl part, you can use a Shindaiwa assembly from a c-25 or c-35 trimmer. I forget the exact number of turns on the air bleed screws to make it run right, but if you need help I can try to find my notes.
Hope you got it running, it's a great old trimmer, a little heavy but a screamer.
Chris
Also, you probably need a primer bulb. Kawasaki trimmer bulb , #49043-2065 works fine. Some unscrupulous people are selling them for way too much. Shop around, you will get a decent price.