I have a Stihl FS74 line trimmer. Made in the early 90's, it was a commercial grade trimmer, and much better than the "throwaway" trimmers I bought before. It's been a good machine, and basically trouble free, until late last summer.
After a few minutes of running, it would die. If I let it sit for a short period of time, it would start again, run for a few minutes and die again. It sufficed for being late in the season, and I knew I would need to find the problem.
Three weeks ago, I removed the tank, changed the fuel lines, and the filter. It started right up, ran for a few minutes and died. To make things worse, gas was dripping from the carburetor. Knowing I either had to rebuild the carburetor, or replace it, I did some web searching for what I needed.
I found a new carburetor, with gaskets, filter, fuel line, primer bulb, and a spark plug for about 20 dollars. I was hesitant to buy online, but thought if it wasn't right, the twenty wouldn't be a big loss. I spent the same amount on the new filter, and fuel line from the Stihl dealer.
The kit came in, I installed the carburetor, primed it, and held my breath. A few pulls and it started, but died, when I tried to speed up the engine. A little adjustment of the jets, and a long afternoon of trimming showed the problems were fixed, and maybe...I can get another thirty years out of the machine. I'll have to cross my finger, because they quit manufacturing it a long, long time ago, and some parts might not be available in the future.