how do you clean a dirty gas tank? - Honda Goldwing Forums
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post #1 of 9 (permalink) Old 01-20-2010, 07:28 PM Thread Starter
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how do you clean a dirty gas tank?

I'm re-building a 1975 GL1000. Does anyone have any tips for cleaning the inside of a dirty gas tank? I mean it's filthy, there is some knobby black corrosion (like rust) on the piping inside, and the bottom of the reserve part of the tank is disgusting with black gooey stuff. I could barely siphon out the old stinky gas, the plastic tube I used kept clogging when I got it too close to the bottom. The tank was a bit more than half full. Norm
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post #2 of 9 (permalink) Old 01-20-2010, 08:16 PM
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I guess you realize you will be removing tank if you haven't already.
I have cleaned a couple of aluminum boat tanks this way.I'm sure there are other techniques,but this worked ok for me.HOT water is a must. Remove all fittings etc. if they will come out.Rinse the tank out really good with hot water.You may or may not see a result.Next,get a can of SeaFoam,seal your fitting holes the best you can.Wooden dowels or such should do.Put the seafoam in and start tilting/turning the tank,moving the solution all around in the tank.If can prop the tank at whatever angle you need to for the really bad areas and let it sit,overnite if need be.Seal it off if doing this to keep from evaporating the solution. If this doesn't get you the result you want,use a VERY dilluted mix of muriatic acid and hot water. i.e. 1cup acid to 1/2 gallon water.This may have to be repeated until tank squeaky clean.Then,final,thourough rinse with the hot water.Put tank in sun,all holes open,to dry out. If rust in tank,i had good luck years ago on an old Kawie with a product called
Kreem. It is an epoxy type product that will coat the inside of the tank,sealing it and stopping rust from getting in your carbs.Good Luck with it.Would like to know how you make out with it,however you decide to clean it.
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post #3 of 9 (permalink) Old 01-20-2010, 10:31 PM
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Step 1
Remove the tank from the motorcycle, if necessary. Refer to the owner's manual on how to do this if you have one, if not, you can apply these basic techniques: Unhook any gas lines, or vacuum lines, depending on the brand of motorcycle. Some motorcycles are equipped with fuel valves on the gas tank. If yours has one, you'll need to remove it. Also remove the low fuel sensor, if your motorcycle has one.

Step 2
Block all of the holes in the motorcycle tank. You can use a short piece of hose clamped onto the fittings on the tank, and closed off at the end with a bolt.

Step 3
Dump the bag of BB's into the motorcycle gas tank and add the 1/2 gallon of diesel fuel. Shake the tank vigorously. The BB's will knock the rust, or any other debris, free and the diesel fuel will keep the particles suspended so that they will dump out.

Step 4
Open the gas tank cap and look inside the tank. If it's not clean enough to suit you, resume shaking until the rust is removed to your satisfaction.

Step 5
Pour out the diesel fuel and BB mixture. Shake the tank to make sure you have removed all of the BBs. Flush the inside of the tank out thoroughly with gasoline to remove all traces of the diesel fuel. Your tank should now be rust free and ready to put back on the motorcycle.
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post #4 of 9 (permalink) Old 01-20-2010, 10:33 PM
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Motorcycle Gas Tank Rust Removal Technique

1. Get a Kreem Fuel Tank Liner. Available at Dennis Kirk, part #3160, $14. You can also order the complete tank prep kit for $26 if desired, but in compliance with CBMMA, I took an even cheaper approach. The kit basically has three parts: part A (acid), part B (MEK), and part C (the liner).
2. Empty the fuel from the tank if it is not already. Remove the petcocks and fuel filters from the tank.
3. Block the openings for the petcocks. I fashioned two stops using a couple layers of heavy corrugated cardboard wrapped in duct tape, cut to fit and held in place with the petcock screws. I sealed them on with cheap silicone sealant (which comes off fairly easily afterward). A wood or metal stop might be more appropriate, but this worked fine for me.
4. If the tank sat with gas in it that evaporated (like mine), clean the tank with a little acetone (or MEK) to remove the worst of the varnish left by the gas.
5. If the tank has large chunks of rust, you may want to add BBs (or chain, etc.) and rotate the tank for a bit to remove the worst of it. Mine didn't need this since it had only small flakes of loose, powdery rust.
6. Mix up a 10% solution of muriatic acid. This is available from most hardware stores as a 20% solution, so just dilute it with an equal amount of water (always add acid to water, not the other way around). I mixed half a gallon of acid with half a gallon of water for my tank. Pour the solution into the tank, taking care not to get any on the paint, unless you plan on repainting. This goes for the acetone or MEK as well.
7. Set the tank on one side for about ten minutes. Then switch to another side for ten minutes... etc. so all the sides get cleaned. I let the whole tank sit with the acid solution for a total of about an hour and a half I think. Look through the gas cap carefully with a flashlight to check the progress periodically. The tank should look brand new inside when done.
8. When all the rust is gone, dump the solution and rinse the tank very thoroughly with water. Immediately clean all inside surfaces with a little acetone or MEK and empty out as much as you can when clean. Any small amount leftover will only slightly thin the liner (which contains MEK anyway). Do not let all the MEK evaporate completely because oxidation will begin right away. Immediately proceed with the next step.
9. Pour in liner according to its directions and follow remainder of directions from liner.
10. The liner may end up a bit lumpy looking, but this is okay, the tank at least sealed and protected. I would recommend doing the whole process outside (for fumes) with a hose handy for diluting any spilled acid. The acid bath may open leaks in the tank if the rust was very severe, so be prepared. If not too large, these can be patched with epoxy filler or by soldering. I was fortunate enough not to have any leaks. I should also mention you may want to check the gasket on your gas cap before you begin any of the process. Mine was so hardened it did not seal properly, but I found a thin rubber gasket at a plumbing supply store for $1.50 which I fit on top of the old gasket for a perfect seal.
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post #5 of 9 (permalink) Old 01-21-2010, 07:56 AM
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hi vintwing. with the tank removed, pour in the contents of a bottle of cheap toilet bowl cleaner, like from dollar general, continually slosh it around an let stand over an over for about 20 minutes. remove the cleaner an observe a nice clean tank. for any rust through holes KREEM is an excellent product (just don't get it on your skin). goodluck
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post #6 of 9 (permalink) Old 01-21-2010, 02:31 PM
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OR take out tank. Take it to reputable radiator shop and have them clean and seal it. Profeesionally done. I have been told the KREEM will eventually flake away causing a repeat of removing the tank.

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post #7 of 9 (permalink) Old 01-21-2010, 07:03 PM Thread Starter
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Thanks for great info. Here's where I'm at now. I got the tank out of the bike today, quite an engineering feat, I had to loosen or remove LOTS of stuff. I have invented some covers for the tank openings, an orange juice lid fit over the big opening on top just right, and I used a short piece of flat steel bar with 2 holes drilled in it to cover the petcock opening. A piece of soft rubber behind it and used the original bolts to hold it on. Now I need to decide which method of cleaning to use. I'm leaning toward starting with the boiling water to loosen that tar-like substance in the very bottom of the tank. Then an acetone rinse, then diluted acid, then Seafoam. There are no perforations in the metal, so I don't think I will use the Kreem.
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post #8 of 9 (permalink) Old 01-21-2010, 11:16 PM
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I inherited an 84 interceptor from my dad who let it sit for two years while enamored with his Harley(probably because he spent all his time fixing it, but I digress). I used the Kreem liner from DK like Joe mentioned and it worked perfectly. Rode it for years with no problems. Sounds like you're on the right track.

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post #9 of 9 (permalink) Old 01-23-2010, 07:40 PM Thread Starter
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I got it nice and clean today. I poured 5 kettles full of boiling water one at a time through the tank. A LOT of stuff came out with each rinse. Next I used muriatic acid mixed 50/50 with hot water, this rinse, which I swished around for about 30 minutes got rid of the rust. I ran a garden hose in the tank for a while after to make sure the acid was gone. Then an acetone rinse (this didn't seem to do much). And now I have some Seafoam liquid in there, I ocassionally swish the tank around. It looks good now, thanks to everyone for the ideas!!!
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