I appreciate the responses. My searches were coming up with stupid stuf. Probably my impatience.
It is a metal tank and I actually haven't looked inside yet. But, it's 30 years old and went from road hard to hardly ridden. Has always had gas in it, not necessarilly full.
It may be fine. Wishful thinking. But since I have a new petcock and carb coming I figured I owe it to myself to make sure it's clean.
I really don't want to dip it because the tank is in pretty good shape on the outside. It has a dent but the paint is good. I didn't realise it but since I have been messing with it the dang thing is a classic. I never realised that there was a whole culture out there that worships these little things. Complete with chrome swingarms and racing cams.
All I know is this little thing put lots of smiles and bruises on lots of little boys and girls and it's fixing to educate another generation.
Thanks