Dan-
Its killer to see your input, and help on the sthil equipment. I have been having fits with the "new" fuel.
In the past when I would just buy Chevron 89 or 92 octane. However in the last year or so, they have started adding ethonal.
In the past I didn't worry about leaving gas in the weedeater, or leaf blower or saw. I had a FS80 (or85) I can't remember, a BG55 and a 310 saw.
First I had a problem with the carb on the FS80, it was like 10 years old, I had never had any problems for the first 10 years. Then alst summer it wouldn't rev up. It would start and idle (wouldn't rev up). Anyway I figured it was time for a new one, (10 years and all) So I unloaded it on CL for parts for 30.00 (whoops)
Anyway, I had the same issue with the leaf blower, the service guy was back logged 3 months. Then my ever reliable 310.
I used it after a big wind storm, poached a real nice cord of fir. Next day it would idle but not rev up. So I said screw it and pulled the carb apart. It seemed to be gummed up inside, I totally disassemble the thing ran some carb and choke cleaner through it reassemblled. It san a little better so I tried it again, and was much more careful the second time. Taking care to blow out the main 'jet" and all the little passages. It runs like new, well with that sucess. I went ahead and tore down the leaf blower carb. And, was able to repair that to.
Anyway, it was killer to have some success, ( I was pretty irritaed with myself, for ruining my tools. However I the past I had not had any problems. Leaving fuel in them, I have two acres, and use my tools all the time. Perhaps they sit idle for 2 weeks at the most)
I am lookin at buying a new little saw, I like the 200 model, however I will probally wimp out and buy the similar saw thats like 350.00