Gas tank questions/options

[Oldmandoom]

Hello all, newbie here. Just picked up a '96 gs500e for cheap with the intention of putting a basket case together.  It's been in a garage for awhile, or so I'm told. From what I can see it just needs a bit of attention. My first project is to get the tank cleaned up.
I had to use a lot of PB blaster to get the key to turn, the cap is a mess. At first I thought rust, but after looking at it and feeling it, I'm inclined to say it's mostly varnish. I'm not too worried about the cap, already ordered a new one for 17 bucks, but I am concerned by two things.
The first is the varnish around the filler opening.
The second thing that concerns me is that when I cleaned the tank out I started with warm wate and some cleaner I found under the sink. I filled the tank up and let it st for a couple hours with the detergent in it. I noticed that water was dripping from the water drain that goes through the tank. Not a stream, but a drop every couple seconds. Makes me wonder if there is a hole in that tube somewhere. Also looks like the tank was possibly red coated at some point.
All that rambling to ask a) Best way to remove varnish and b) Could red coating the tank again solve that possible pinhole in the water drain tube? I have pics but I need to figure out how to get them to the right size. Thanks in advance for any advice

[Oldmandoom]

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[Falken Hawke]

The varnish on the filler is only a problem if you want it to be one.  I've only been able to remove varnish with an abrasive but I haven't tried submerging parts into a carburetor cleaner dip either.

To verify the drain tube is leaking, seal off one side and use a rubber tip blowgun attachment for a compressor on the other while looking inside the tank when full of a clear liquid.  If using water, rinse with Acetone after draining.  If a compressor is not available, use a can of compressed air for computers and build up a stopper on the straw end with electrical tape to the drain tube.  However, if the leak is really small, this may not be enough pressure to indicate a leak.

There is a coating in the fuel tank but without knowing what it is, it isn't known if another coating will bond to it.  Fixing a leak on the drain tube will be a challenge so I would first try by applying a coating directly to the area determined to be the leak and hope the coating bonds.

Otherwise, provided the leak is near enough to the filler hole, the tube will have to be cleaned thoroughly and recoated.  If after cleaning the leak is too large for a coating, a two-part fuel resistant epoxy can be used.  Just be careful not to let it enter the hole and block the drain.  Masking tape can be used to prevent that.

The worst case would be having to cut open the tank for access.  If it comes to that, it will probably be cheaper to replace the tank.

[Oldmandoom]

Falken Hawk thank you for the reply.

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