Rust in gas tank

Hi, new to forum. Acquired a 1986 r80rt that’s been sitting for 30 + years. Looks like the gas tank could have rust or at least varnish and gunk collected. Was wondering what the best cleaning product is without damaging the tank. Anyone have a good solution.






1976 r90/6
1998 k1200rs
2000 r1100s
1998 r1100gs
2007 r1200r

Welcome to the forum, gracie! I hope you can take care of the neglect on the tank!

First, look through some of the threads in the Similar Threads pane at the bottom of the screen. Those will contain previous discussions to get you started.

Next, I'd look at these pages on Snowbum's website...already having an Airhead, you're likely familiar with his "verbose" style of writing. Good information there.

https://bmwmotorcycletech.info/fuelmiscl.htm - a little ways down the page, #6 begins discussion about cleaning

https://bmwmotorcycletech.info/chemicalsetc.htm - nearer the bottom of the page, #19 additional info on tanks and cleaning

I used Red-Kote gas tank sealer on an old farm tractor last fall. Clean the tank out really well. Some steel balls, or a short length of chain to knock off the big chunks of rust and other things. Clean the tank out with a detergent and water. I used Simple Green and rinsed it out. Let it air dry.

Add the Red-Kote swish it around in the tank. Let the excess drain out.

http://damonq.com/red-kote.html

Cleaning & sealing tank

I’ve done many gas steel gas tanks by filling them with a product called EvapO Rust. Leave tank this way for a few days. You can put some nuts and small bolts inside and shake tank around from time to time, but not necessary. Drain the EvapORust back into its container and save, it can be reused. Meanwhile get a motorcycle tank package of Caswell Epoxy gas tank sealer. Read directions completely. Mix the 2 part epoxy and pour into tank. Follow directions. It’s very easy, gives perfect results and seems to last forever.

I watched a video about using vinegar to remove the rust. I can't remember, nor can I find the link to the video I watched. However, you can search for similar videos on Youtube, etc. I still need to do this, but I waiting to get a GS first.

POR-15 has an EXCELENT SYSTEM to use that lasts for years. At least check it out...........Good luck......

Clean first

If it were me, I would take steps first to clean the tank out with something that would not tear up any liner. This could be kerosene, parts cleaner, carb cleaner or some kind of cleaner as listed in snowbum's writings. I would not use nuts and bolts, or any kind of material that could damage the liner.

The reason I say this is because the original liner in the tanks is pretty darn good and taking steps to clean remove and reseal might just be making more work than is needed. Don't jump on the new tank liner band wagon until after the old gas and varnish is cleaned out.

A good flashlight with an inspection mirror will let you see down into the bottom of the tank after it is cleaned. If the liner is good, carry on, you saved a bit of cash and work. If there is rust or the liner is shot, then, you will either reline with some product or even have to go to a shop to have the tank repaired depending on how bad it is.

Good luck, St.

hstender said:

I’ve done many gas steel gas tanks by filling them with a product called EvapO Rust. Leave tank this way for a few days. You can put some nuts and small bolts inside and shake tank around from time to time, but not necessary. Drain the EvapORust back into its container and save, it can be reused. Meanwhile get a motorcycle tank package of Caswell Epoxy gas tank sealer. Read directions completely. Mix the 2 part epoxy and pour into tank. Follow directions. It’s very easy, gives perfect results and seems to last forever.

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I used EvapO Rust to clean up some sockets and wrenches. Then I coated them in some WD40. After that I changed storage solutions. It is great stuff for preserving tools.

I think that the biggest problem you are going to have is that 86 airheads have that infernal emission control funnel under the gas cap. It not only has a tiny hole at the bottom, but the hole has a spring loaded flap. I have an 86 R80 and I had Max BMW in NH remove the funnel (they used a die grinder), clean the tank and recoat it. It was expensive, but I think that the cost reasonably reflected the effort required. It had the side benefit of giving me a bit more usable fuel capacity as well.

I don't think there is anything magic in what they did and anyone with patience and a small grinder could probably do the job. Max also has a machine they built to agitate the tank to get rid of the rust and the old coating. I was fairly sure that their machine would have more patience with that step than I would have. I gave it a lot of thought and decided that the effort and the need to dispose of hazardous chemicals made farming the work out the best option.

hstender said:

I’ve done many gas steel gas tanks by filling them with a product called EvapO Rust. Leave tank this way for a few days. You can put some nuts and small bolts inside and shake tank around from time to time, but not necessary. Drain the EvapORust back into its container and save, it can be reused. Meanwhile get a motorcycle tank package of Caswell Epoxy gas tank sealer. Read directions completely. Mix the 2 part epoxy and pour into tank. Follow directions. It’s very easy, gives perfect results and seems to last forever.

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+1 on Evaporust. I haven't used it on a gas tank, but it's works better than Naval Jelly and it isn't toxic or corrosive.

Thx for the replies. I’ve been looking through the internet and the other threads on the forum. I’ve decided that I’m not a fan of putting bolts or ball bearings in the tank. I don’t want put more things in the tank that could be a hassle to remove later. I’m trying to get the petcock plastic pickup tube out of the tank now and the top filler flap is not making it easy. Since it’s midwinter and I have a lot of time. I’m going to run some kerosene through first just to see how much more crud comes out. I’m hoping it’s just varnish related old gas and not too much liner. The bike only has 2200 miles on it but it did sit in a barn for 30 plus years. Lots of other things to go through before I decide to start it up. Thinking of chucking the big fairing and making it more standard since the bike fell over numerous times from its centerstand and the fairing has lots of scrapes. Was interested to see where Max bmw cut out the filler flap on top of the tank. Hey Anyname could you post a pic of your top filler tube to see where they made the cut. Thx and Happy new year

Nuts & bolts

gracie said:

Thx for the replies. I’ve been looking through the internet and the other threads on the forum. I’ve decided that I’m not a fan of putting bolts or ball bearings in the tank. I don’t want put more things in the tank that could be a hassle to remove later. I’m trying to get the petcock plastic pickup tube out of the tank now and the top filler flap is not making it easy. Since it’s midwinter and I have a lot of time. I’m going to run some kerosene through first just to see how much more crud comes out. I’m hoping it’s just varnish related old gas and not too much liner. The bike only has 2200 miles on it but it did sit in a barn for 30 plus years. Lots of other things to go through before I decide to start it up. Thinking of chucking the big fairing and making it more standard since the bike fell over numerous times from its centerstand and the fairing has lots of scrapes. Was interested to see where Max bmw cut out the filler flap on top of the tank. Hey Anyname could you post a pic of your top filler tube to see where they made the cut. Thx and Happy new year

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Just to clarify a few things about tank cleaning. 1) although I mentioned that you can use small nuts and bolts, I personally don’t use them. I don’t recommend they, I only offered that as something that can be done. 2) I’ve cleaned and sealed many, many tanks in my shop. I’ve had to remove failed POR liners and Kreem liners. I’ve never had to redo a tank lined with Red Kote. The process that works best, by far, for me is Caswell Epoxy gas tank liner. I have tried using vinegar in the distant past and it didn’t work at all, for me. Just created more problems. The process is pretty easy, just be patient, take your time, read & follow directions.

gracie said:

Thx for the replies. I’ve been looking through the internet and the other threads on the forum. I’ve decided that I’m not a fan of putting bolts or ball bearings in the tank. I don’t want put more things in the tank that could be a hassle to remove later. I’m trying to get the petcock plastic pickup tube out of the tank now and the top filler flap is not making it easy. Since it’s midwinter and I have a lot of time. I’m going to run some kerosene through first just to see how much more crud comes out. I’m hoping it’s just varnish related old gas and not too much liner. The bike only has 2200 miles on it but it did sit in a barn for 30 plus years. Lots of other things to go through before I decide to start it up. Thinking of chucking the big fairing and making it more standard since the bike fell over numerous times from its centerstand and the fairing has lots of scrapes. Was interested to see where Max bmw cut out the filler flap on top of the tank. Hey Anyname could you post a pic of your top filler tube to see where they made the cut. Thx and Happy new year

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Here you go. I measured the distance from the top of the filler neck to where the neck was cut. It's almost exactly 1 3/8". I really hated that funnel and the flap.

flapectomy

One of the best things I've done to my '92 R100RS is a "flapectomy", I really hated filling the tank at the gas station before that -it would take forever to get the last quart or so in. Now it fills like any other tank. This write up is pretty good:

http://www.gunsmoke.com/motorcycling/r100rt/flapectomy/index.html

I actually filled the tank almost completely with water during the cutting process, I just hate it when residual gas vapor in the tank explodes from a spark and burns down your shop.

Adam

gracie said:

Was wondering what the best cleaning product is without damaging the tank. Anyone have a good solution.

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What the chemistry teacher told me and it worked, plus it cost me practically nothing to get some heavy rust out of a Honda XL 175 gas tank.

Heavy Duty Radiator Cleaner. This was the white crystal type in a bottle.

I drained the gas tank, washed it out with detergent, drained it again, filled half the gas tank with hot water and topped it up with boiling water (this speeds up the chemical reaction). Added the Heavy Duty Rad Cleaner to the nearly full gas tank and let it sit. I did this twice and the inside was like new. I never coated the inside. The gas kept it rust free. Keep any spills off the painted surfaces, so keep a garden hose handy.

GlobalRider said:

What the chemistry teacher told me and it worked, plus it cost me practically nothing to get some heavy rust out of a Honda XL 175 gas tank.

Heavy Duty Radiator Cleaner. This was the white crystal type in a bottle.

I drained the gas tank, washed it out with detergent, drained it again, filled half the gas tank with hot water and topped it up with boiling water (this speeds up the chemical reaction). Added the Heavy Duty Rad Cleaner to the nearly full gas tank and let it sit. I did this twice and the inside was like new. I never coated the inside. The gas kept it rust free. Keep any spills off the painted surfaces, so keep a garden hose handy.

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Did you have do/use anything to neutralize the radiator cleaner? Also what about disposal. It seems like it would be hazardous waste.

On a side note. I spent my youth riding a mid '70's Honda XL 175. I learned on a XL 70. That brings back memories.

88bmwjeff said:

Did you have do/use anything to neutralize the radiator cleaner? Also what about disposal. It seems like it would be hazardous waste.

On a side note. I spent my youth riding a mid '70's Honda XL 175. I learned on a XL 70. That brings back memories.

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The larger bottle of Heavy Duty Radiator Cleaner has a smalled bottle in it with a neutralizer. Maybe baking soda? I did this in the driveway with lots of water running to dilute it. The same thing would happen if it was used in a rad. This would have been in 1986.

I believe the XL 175 was a 1978 model. It had a black gas tank with red accents. I bought it used for $175, so $1/cc from an old Spitfire pilot. That got use talking. It would not run (carb) but it got a going over once I had it.

My first and also new motorcycle was a 1975 Honda MT 125. I had it for 3 months before I moved to a new 1975 CB 400F Super Sport.

Removed liner

I bought my 1986 R80RT from a friend who had it for 20 years. The 2nd time I rode it the left carb peed gas on my boot. I took the float bowl off and found red flakes in it. Consulted this forum and was told it was the liner flaking off.
After watching You Tubes and reading on line I decided to used BBs and LOTS of shaking and rinsing. It took many shake rinse repeats to get all of the liner out. I used Evaporust to take care of flash rust before I put the tank on my bike and filled it with gas. I chose to not put another liner in after reading stories of people putting in liners that didn’t stick well and they had to remove the new liner. If you think it’s a PITA to remove it once, do it twice! I drained and took off my tank yesterday to replace the headlight relay under it yesterday. I have a screen in my 6 gallon gas jug and there were no signs of liner, and this is two years after removing it. If you chose to not reline the tank you have to keep it full of gas or rust will start growing. Rust never sleeps. I also used Dawn and boiling water with more shaking after removing the BBS each time. Then rinse with fresh water. I did it in summer so I did all of the rinsing in the yard with the hose. Revzilla has a good explanation online of the process I used, which is where I got the idea. If I had to do it again I would pay to have the liner removed and replaced. It was a PITA job that took many days to do. Good luck and have fun! And I used needle nose pliers to twist and rip out the flap in the filler neck. I then installed a billet aluminum Monza style gas cap, made for our BMW model by Motone Customs. Groovy!!





1976 r90/6
1998 k1200rs
2000 r1100s
1998 r1100gs
2007 r1200r[/QUOTE]

On steel gas tanks that are not going to move for a while (storage), I put some Mystery Oil in with the gas and give it a shake. I’ve used non-synthetic 2-stroke fuel mix oil as well.
It leaves a bit of a coating that helps.
OM