After several recommendations from members of a Triumph forum I've just used the large Caswell Tank Sealer kit on my 1997 Thunderbird (tank capacity 15 litres). Firstly it was treated with Rusty Metal, then cleaned and dried. As per instructions I made sure the temperature was within range, the products measured correctly and mixed thoroughly. I rotated the tank slowly in all directions, then excess sealer left to drain. Upon inspection it has left a nice smooth, shiny coating throughout the tank except for the overflow tube which, apart from a few drops, is still bare (this can be seen in pics: running near to the top of the tank, looking down through the petcock hole). Although in reality it could easily be overlooked due to the shape of the tank and it's small openings.
Leaving the tank like this will not fix my current 'rust in the fuel' problem, plus I'm guessing may lead to things far worse (fuel working it's way down in between the sealer and the tank....). Definitely not the desired result after spending a considerable amount of money on this kit.
Have you heard of similar issues with internal structures not getting covered before?
More importantly, what can now be done to fix this?
Any help would be greatly appreciated.