I have a 2005 RK and the tank on my bike is lined. When I bought the bike there was a dent in the tank. During the repair process I got some sanding dust in the tank, I decided to rinse the tank out with water and let it sit to dry out. Big mistake... the moisture attacked the liner and caused it to wrinkle up and fall off in large flakes.
It was perfect before the water and only took overnight to be screwed.

 

If water causes the problem in the first place, I wonder if just filling the tank with water for a couple days might loosen that stuff up some more. If it had a good result, might be a matter of water/chain scrub cycles till you got it cleaned out. I'm going to have to go through this with my 883 one of these days, seems to have a fine layer of rust all over the insides - I'm guessing it doesn't have HD liner in it - but then it's an unknown maker gas tank, too.

Mikey1450 - thanks for the POR-15 tip, I've been looking into those tank kits, haven't run across that brand before.

 

UPDATE:
Bought the sash chain recommended by TwiZted Biker in post #4 and spent today sloshing it around inside the tank. It works.


Big lesson I learned right off is to remove the float assembly from the left side of the tank before doing any of this. The chain got tangled up in the float assembly right away and it was an ordeal to get it loose. I had to destroy the float assembly in order to get it out of the small hole in the top of the tank, but probably needed a new one anyway since it was exposed to the stripper for several days. To avoid this, plan on removing the float assembly (and possibly destroying it by doing so) first thing before doing any of this.


There is also a metal tube on the left side welded from the top to the bottom of the tank that houses and protects the two wires that feed the fuel gauge from the fuel. The chain tries to wrap around that too, but it easily untangled with more shaking.


My arms hurt now and I got a little winded several times shaking the tank for 5 minute intervals, but the chain is working. I am using the RIGID flexible-wand lighted inspection camera ($79 from Home Depot) that I mentioned in my OP to see deep into the tank to target remaining flakes and then tilting the tank so that the chain is scrubbing those areas. This would be impossible without the lighted inspection camera. Slowly, but surely, that old liner is being completely eliminated.


If you did not read my initial post carefully and if you have a tank that was lined by the HD factory and the liner is flaking (bet you it is, even if you aren't aware of it YET), let me repeat that the first effective step that I took was to pour a quart of POR-Strip (not POR-15) into the tank and set the tank on a table propped up at many angles, letting it sit for several hours in each position, over and over again. This, followed by the chain scrubbing after completely flushing the stripper repeatedly with water is the key to getting the old liner totally out.


If you do not plan to recoat the tank with a new liner product, you could just use a gallon of apple cider vinegar to slosh around to remove the rust and crud from the bottom of the tank, flush with baking soda/water solution followed by several water flushes, and complete with the chain scrubbing routine followed by a good "blow-out" with compressed air. This would probably get the tank surface suitable for reinstall, but expect surface rust to reappear quickly (instantly) if you do no use a liner coating product.


If you decide to recoat with a new liner, it is imperative to remove all of the old HD liner before recoating. Here's where things get ugly.


Let me tell you, and I do not exaggerate, this is one of the worst jobs that I have ever attempted. It is epically unpleasant work from beginning to end!


First, you must remove the float assembly and possibly destroy it doing so. Second, you are working with a very toxic chemical, so industrial skin protection, googles, and a gas odor-rated respirator are mandatory. Third, you must fanatically protect the paint on the outside of the tank with Saran wrap, aluminum foil and duct tape and plug all openings (filler, petcock, crossover, vent tube) completely while you are working with the stripper in order to preserve your paint job. Fourth, you will need re-sealable metal cans to pour the nasty flushed goop into (not a sink!) and I don't yet know what the heck I am going to do with those containers now. Fifth, the chain scrubbing takes several hours of effort and determination. Sixth, plan on spending about $200 for the inspection camera, POR-Strip, Saran wrap, aluminum foil, duct tape, rubber and cork plugs, 10 feet of sash chain, plus whatever a new HD tank float costs if you destroy it getting it out as I did.


Wish I had a less harrowing report for you, but at least the worst of this is behind me now and I am ready to recoat with a new tank liner. No more rust flakes and liner pieces clogging my petcock screen and settling in the bottom of my carb's float bowl.

 

Here's another old school remedy for getting moisture out of tanks after rinses or repairs , isopropyl or denatured alcohol absorbs the water off moist surfaces and seams. Used to dump it into gas tanks that had water problems back in the 70's before gas came with ethanol. Half gal. cans in any paint dept. at the hardware stores.

Seal up the tank add a cup, do the shake/swish thing for a bit paying attention to the inside seam, drain, blow it out and repeat , tanks bone dry and no residue and it doesn't bother the paint.

I've repaired & welded more cracked tanks than I care to remember , takes some elbow grease but the methods are time proven and work.

 

Once the inside of the tank was completely stripped and flushed, I treated it with a product called OSPHO, available from ACE Hardware. This stuff is the bomb! Somehow it completely removes surface rust and transforms the iron/steel surface such that it will no longer rust. No need for a new tank liner that may put me back where I started in a few years.


The tank is now back on my bike and looks good as new, inside and out. I did install a fuel filter right after the petcock as a safety precaution, but the screen has remained completely debris free as has my carb.


Man, this has been one for the books...

 

Haven't used their gas tank stuff yet but their other products have been great when i used 'em. {7.3 oil pan repair]

 

I just used a can of premium Zip Strip [11.00 qt--Its fairly thick and I just keep slow rolling it to keep it as wet as possible

 

I have an 03 I am now dealing with this issue....how is your no recoating of the tank holding up? I am looking at the prices of everything and thinking it might just be easier/cheaper to replace my tank (I don't think the custom paint is going to servive the process and I also found rust attacking the fuel guage bung). if I rework the old tank and then have to repaint...may as well just replace the whole thing. An update would go a long way for me on this.. thanks in advance.

 

I just bought a 92 fxr and noticed when I pulled the gas cap that the yellow liner is flaking off. A good bit is gone and little to no rust. I have been riding it a good bit and no problems yet. I am thinking about stripping it and treating with OSPHO.
How did you treat with ospho? Is it a painted on type of product. Did you swish it around in the tank? Curious I may wait until the season is over and just run the tank how it is keeping it full as the flakes so far do not seem to have affected performance for previous owner or myself YET.

 

Chances are that trying to remove liners and recoat the inside of your tank will ruin the outside paint. Fumes and drips during the process are hard on paint.