cleaned it up again better, flushed rust out of tank again, also better - not perfect, but way better. might have time to set it up back on moped and test tank and petcock again tomorrow.
I think if one was so inclined it would be relatively simple to cut a new little rubber washer by hand. kind of like an easy arts and crafts type work. since this is fresh in my mind, the pieces to keep track of are
* the washer that fits between the petcock and the tanks. a basic washer, could probably get a new one at any hardware store for .15 cents if leaking
inside the petcock
* the rubber washer with the 3 holes
* then a small metal washer with a couple toes that keep it from turning
* the piece that rotates and directs the flow for the holes next
* a relatively strong spring
* behind the little arm of the handle that fits into the slot in the direction flow piece is what looks like a nylon washer
fit slot on gas flow piece to slot on handle piece - and tighten down, the spring pressure makes this a little tricky
think this was all the pieces. It didn't seem to leak, so was worth taking a shot at cleaning it up again.