Once you sort out the rust are you going to solder the holes up?
Yep, will try to. There's quite a few pinhole-sized holes. If I can't solder, I might have to look into a fuel-resistant putty and fill the holes.
G'day Widget,
You could just put the tank in a bucket of white vinegar for a couple of weeks ,that would remove all the rust then you
would have to neutralize the acid to stop the metal rusting again.This would save taking the tank apart.
Cheers
Max.
Thanks Max. I used some double-strength vinegar, which has helped some, but would need to soak longer. The holes make it a little hard as can't soak that area, the vinegar leaks through

. I tried separating the tank, but I can't undo the folds, which is a shame as that would make it much much easier to fix the inside.