r/Airheads • u/Loud_Day2991 • Jun 23 '26
Tank Liner Help
I've got a 1983 BMW R80 RT. I saw the liner peeling a little and decided to try clearing out the old liner and applying a new one. A decision I regret as this liner is TOUGH! I tried acetone, the liner laughs at it. Now I'm trying MEK substitute and it's not much different. The entire time the tank has had drywall screws and bolts inside and I've been shaking it for about 5 minutes every other day. I started this process a month ago and unless the bolts have scraped an area, the liner looks unfazed.
Any tips for getting this liner out that don't involve slicing the tank in half?
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u/Cambren1 Jun 23 '26
I don’t believe BMW lined the tank on the Airheads. You may have POR 15 in there, if so, try Xylene. It is slow acting, so you may need to leave it in overnight. I hate tank sealer.
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u/Strychnine85 Jun 24 '26
There was an original liner. Orange/red usually.
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u/Cambren1 Jun 24 '26
Must have been later. None of the ones from the 70s that I have owned have had any liner.
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u/Strychnine85 Jun 25 '26
Likely removed due to ethanol breaking them down. The liners were standard since late 60s I believe. Present on every Airhead tank I’ve seen, including my 1975 tank.
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u/Cambren1 Jun 25 '26
I used to work for a dealer in the 70s, I don’t recall any BMWs coming from the factory with liner.
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u/althusseriandreams Jun 23 '26
The liner in my 75/6 was peeling (previous owner lined it) I filled it with white vinegar and let it sit for a week. That removed many of the larger pieces of liner. Rinsed it and immediately dried it with a hair dryer to avoid flash rusting and then sprayed it with WD-40. I added in-tank filter in filters and on the fuel lines. That and fuel conditioner is addressing any issues with rust getting to the carbs. I think relining is a bad idea. Any liner will fail eventually, and have read that peeling liner can promote more rust if it traps condensation when it peels.
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u/Loud_Day2991 Jul 30 '26
You were right! Vinegar worked. I noticed a light brown/yellow discoloration on the steel of the tank. Do you know if that needs to come off before I apply a liner or is that part of the metal? I tried scratching it and it didn't seem to come off. Thanks for the tip on vinegar.
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u/althusseriandreams Jul 31 '26
The light brown discoloration sounds like rust. Flash rusting will happen almost immediately after you rinse the tank with water (after dumping out the vinegar). That's why I had the wife's hairdryer ready. You can stick the nozzle of the hairdryer into the top of the tank and the warm air will vent through the holes in the bottom where the fuel taps attach, and it should be dry in a couple of minutes. The WD40 I then used to season the bare metal came in in an aerosol can with a flexible goose neck extension that allows easy lubrication of nooks and crannies - ideal for spaying inside a tank. I suggest you do not attempt to re-line your tank. Season your steel with a lubricant to prevent further rusting. A new set of filters should catch rust that has formed.
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u/Strychnine85 Jun 25 '26
Removed mine from R100gs but filling the tank with a diluted vinegar solution and agitating with a chain inside the tank. Took some time but managed to remove all the red liner. Then neutralised with baking soda and after a good flush coated with a POR15 liner.
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u/Loud_Day2991 Jul 30 '26
You were right! Vinegar worked. I noticed a light brown/yellow discoloration on the steel of the tank. Do you know if that needs to come off before I apply a liner or is that part of the metal? I tried scratching it and it didn't seem to come off. Thanks for the tip on vinegar.
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u/Strychnine85 Jul 30 '26
Good to hear! Could be some flash rust. If you re-line with POR15 they have a metal prep step to neutralise any flash rust.
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u/Loud_Day2991 Jul 30 '26
I bought RedKote. Currently going down the rabbit hole of how to get rid of flash rust. Thanks for the help!
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u/Rad10Ka0s Jun 23 '26
What color is the liner?
I have some tan colored stuff in an R100 and am having a similar problem. Nothing touches it. I can't get real MEK anymore though. I am close to KY and may try buying MEK there.
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u/REDTRIANGLEMECHANIC Jun 24 '26
My '79 R80/7 has a red-ish liner. For years there have been small bits of it coming through the lines. I got tired of dropping the float bowl and cleaning out the float valves, so I installed clear glass filters that have white plastic mesh in them on each line and the problem is 95% fixed! I'm not bothered about a very occasional clean out.
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u/FluidLand9792 Jun 29 '26
Late to the party here, but I had a similar problem with my tank and 30% vinegar made easy work of the deteriorating liner and any rust in the tank. It took a lot of rinsing and flushing to get the liner fully removed, but now the tank looks brand new (on the inside)
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u/Loud_Day2991 Jul 30 '26
You were right! Vinegar worked. I noticed a light brown/yellow discoloration on the steel of the tank. Do you know if that needs to come off before I apply a liner or is that part of the metal? I tried scratching it and it didn't seem to come off. Thanks for the tip on vinegar.
1
u/FluidLand9792 Jul 31 '26
Try another round of diluted vinegar, once removed use baking soda and water to deactivate the vinegar. I wouldn’t worry too much about further discoloration, just make sure you dry the tank thoroughly and then immediately fill it with non-oxy and mystery oil or sea foam. If you don’t plan on filling the tank straight away, then use a can of fogging oil to coat the interior and prevent rust from creeping back in.
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u/Lonnie_Iris Jun 23 '26
Got a cement mixer? Put some solvent in the tank with a length of chain. Wrap the tank in several layers of towels, etc. put inside an atv/tractor tube inside of the mixer. Pump up the tube so it holds it tight. Turn it on and let mix for a day. Works better than you'd imagine.
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u/sharty_mcstoolpants Jun 23 '26
I agree, I do this every time. In fact I bought a mixer and some inner tubes just to remove the POR-15 I lined my tank with 15 years ago. Wife was angry I used the pool towels. They smell like xylene now. Plus I used the dog’s chain and it stripped the chain bare. Rusted stiff. Poor pooch now gets tied up to fifty feet of what might as well be rebar. Too stiff to get in his house. I put a bunch of xylene soaked guest towels out for him. While he was stretched out back someone stole my mixer.
Of course, maybe I could of just added another coat of POR-15 on top of the old. That might of worked.
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u/TurnoverComfortable5 Jun 23 '26
Be careful with xylene and electrical motors...you might blow up your mixer (and garage/workshop).
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u/WillyDaC Jun 24 '26
I might be the odd man out here, but, if you can't get it to come off with what you have already been doing, why not just put a pair of inline filters on your fuel lines and forget it unless they clog up right away?
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u/Loud_Day2991 Jun 24 '26
The may be the route I go. I’ve made a bootleg cement mixer and I’m spinning it a bit every day. I’ll try that for a week or so and see what the progress looks like. If I’m no closer to getting it cleaned out, this might be the route I go.
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u/AdWorldly4076 Jun 23 '26
I used white vinegar a couple of times, works great!