I was worried that my tank might have debris in it so I decided to change the fuel filter. I pulled the fuel cap and inlet neck off and looked inside. Much to my dismay I saw a great deal of rust inside. This is quite common of Ducs of this vintage, I cleaned out all of the rust and it is clear that I must seal the inside of the tank. There is a company called POR-15 that sells a kit for just this very problem. I will do it as soon as I get the materials from the company.
Another common problem is that the gasket under the fuel inlet rots out. Mine of course was bad so I swapped it out. This is not as easy as it looks! The gasket needs to be stretched just right to make a nice seal. After a few tries I came up with a technique of getting the inlet almost all the way seated and then putting the gasket on from the top. It looks great but I will be taking it out again soon to do the tank sealing.
Didn't ride, just cranked her up to be sure she runs.
Inserting the fuel pump with a new filter. Ugh, rust...
New fuel inlet gasket - not as easy at it looks.