Sounds like the fuel line might have been a problem all the wile. Air leaks are killers and can drive you nuts. It appears you have plenty of other good saws to use. So I would spend some time on this saw and test everything thoroughly with a vacuum/pressure gauge. There are so many rubber surfaces that wear, shrink and crack that it’s possible on an old saw to have multiple problems at once. But the critical thing is you must find all the problems before you consider fixing that top end. The 028 is a Classic and worth fixing. Plus it’s another good pony in a strong stable of saws.