same as a regular tank cleaning.
1.plug up petcock spout.(make sure you take off petcock and drain gas.)
2. add prolly a liter or so of muratic acid.
3 add a jumbaly(yes i prolly made this word up) of washers bolts nuts random metal objects. put gas cap on.
get a friend.
4. shake the shit out of your maxi as much as possible.
5 drain muratic acid, and de-activate it safely.
-OR- you get a fuel filter for 3 bucks from 1977. that will most likely work too. depends on how bad your tank is.