In that case I can see where you'd need one. Come to think of it I don't believe my fathers 601 has a sediment bowl. He's never had a problem either.
One thing you might could try is using a large coffee filter in the funnel. I think they'd tolerate gas but it'd take a long time to fill the tractor through a filter. You can get store brand coffee filters in cone/bowl shapes that are quite large. But that is not w/o it's problems either.