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Discussion Starter #1
97 SS/CR. Went to install a new battery, tipped the gastank back and gas started to leak, I think from the rear left hand side corner. Can't see from where, possibly the seam (?).

Wondering if it could have rusted out. It sits through Boston winters with a full tank and STABIL, but maybe water came out of solution and sat at the bottom (in these E10 days?). I know that's a thing with older BMW airheads, but never considered it for the Duck.

Anybody run into before?

Thanks gang. - BrianK
 

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Quite possible, but odd that it started when you tipped the tank up. Perhaps flexing near the hinge caused the leak to start. Or sometimes fuel will leak out the cap area and drain down through the cap drain line in the bottom of the tank. Or the internal drain hose came loose and when you tipped the tank back fuel started to run out that line. There is a sticky at the top of this forum for repairing rusting / leaking gas tanks. Personally, I would avoid lining the tank unless necessary and would see if it can be repaired by welding. Many have had good luck with tank liners, but I think the preferred liner material has changed due to fuel interraction issues and I don't know what the preferred material is. A forum search should help.
 

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Discussion Starter #3
Thanks I will check out that thread and look into the source of the leak a bit more when the new battery arrives. Was just wondering if this was common in this model as it apparently is with airheads.

I agree re lining although I am not above giving it a shot....

I'll try to remember to report back with findings in case it may help others.

Thanks again.
 

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anything with a steel tank will rust. i see a lot with at least the start of bad rusting in them due to water. the left hand side lowest point is the worst, and lots of these tanks - monster, st, sbk in particular, have nice spots for it to collect and rust. the 400ss i bought was rusted out both sides at the bottom.

i had a guzzi daytona in once that had bubbling paint on the underside of the tank - they have large flat areas on either side of the spine. but it wasn't leaking. once i'd drained all the water out of it, it started leaking fuel as the surface tension of the water, under the fuel, was plugging the holes. i thought that was pretty funny. i think the owner was going the "it wasn't leaking before i bought it to you" line. to which i probably said "put some water in it then."
 

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First thing is -what does the inside of the tank look like? Pull the fuel cap & flange drain the tank and look inside you should be able to see if it is rusty very easy. --I did clean & line the tank on my 91 900SS and I used the POR 15 kit to do this tank, On BMW's I normally use Red Coat. My tank was not leaking and had what I would call superficial surface rust and smegma from sitting for 18 years with a little fuel in it. When I cleaned and prepped it before putting the liner in I looked and not even any pitting was visible,so I was a good tank to work with. But I would look at what you have carefully-is there any bubbling of paint anywhere on the tank especially the bottom rear? -something to check just because it's there--Is the drain bolt tight? -it's rear left side you never know
 

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If it does not leak when down but does with a full tank when up you need to check first that it is not leaking out the gas cap. It is common that with a full tank and tipped up you will leak out the cap ad it will run down to the low point. Verify this before ever coating a tank and avoid coating if possible, what seals today fails tomorrow. If you do have a bad tank you have to seal it somehow but there is NO coating I have not seen fail and once coated you are not going to be happy if it leaks again.
 

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Black rubber gasket around the filler cap. I had the same issue. Replaced the green o-ring as well. Black gasket is difficult to install. You need four hands to hold it in place on the filler housing. It can be done though.
 

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The black gasket is not for keeping fuel in the tank, it keeps water and crud out of the space between the cap carrier and the tank. The green Viton O-ring seals the cap carrier to the tank. Locking caps will occasionally start to leak through the lock cylinder once they age. For those of us that installed an aftermarket "race" cap like Oberon, they usually have an air hole and leak by "design" if the tank is tipped up and full.
 

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Discussion Starter #9
It does appear to be the gas cap, as it only leaks when (i) full and (ii) tipped back to almost vertical. If either of those conditions isn't met, no leak. But I cannot for the life of me see anything but fuel dripping off the bottom left corner when those conditions are met. Anyway, easy enough to avoid I guess.

Thanks for your help folks. - BrianK
 
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