I picked up a project 900ssie. I had intended to put my spare slightly secondhand ie tank on it. But I came across a carbie tank and thought I might try that. I removed the cap, to find it not too bad underneath/inside. What I don’t understand is the internal plumbing. The pump seems to be connected to the drain. The delivery is just a tap connected to the internal pipe work. The drains on the cap are just linked together. Anyone know which way round they should be?
I think the pump should be connected to the mandata delivery Which is the one not connected in this photo
I went the whole hog and rebuilt a 1000SSie with a full set of 900SL style bodywork: https://www.ducatiforum.co.uk/threads/1000ssie-ds-900sl-hybrid.84101/ The tank conversion starts at post #6, but most of what you need is in #7. I believe the 1000SSie frame etc is identical to the 900SSie so it should fit the same.
Looking at what you did and what has been done to this tank, I get the impression that you did it right and this has been modified. There were blocks of sponge in the tank, so I am thinking race bike.