I flush my tanks with water after soaking with vinegar.
hold the moped upside down with the hose stuck in the gas tank cap or have some spray the hose into the cap.
Make sure to let us soak for a good week.
All the heavy stuff comes out at the end so Ull have to flush it multiple times.
If your trying to flush thrue the petcock hole it’s just frustrating, to small and takes for ever (edited)