We have a few old stihl products in the garage that haven't been touched for a couple of years, i've been trying to start em up. the HS 45 hedge trimmer has been confusing to me. before I cleaned the carburetor it wouldn't start at all. after it was cleaned, it ran fine for about 3 minutes, then it shut down and wouldn't start again. confused, i went into the carburetor and fiddled with the black screw thingies, and then tested it out, sometimes it started then died, sometimes it did nothing. anyone know what is happening with it? thanks.