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Thread: Dorsoduro swollen tank storage

  1. #1
    apriliaforum Member Ametts21's Avatar
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    Dorsoduro swollen tank storage

    I know the swollen tank topic has been discussed but couldn't really find the answer I was after. My fairing mounting holes are very ovaled and it takes some coaxing to get them back on the bike and my key is not centered so obviously my tank has swollen. I put gas in the other day and added stabil to store for winter not thinking about this issue. Is it best to drain out and store with empty tank? Will the tank shrink back down?

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    As per:

    http://www.apriliaforum.com/forums/a.../t-241922.html

    The swelling is due to moisture getting into the plastic (polymer - usually nylon), which first clings to the alcohol content in the fuel, so the additive would have to be specifically formulated for it to have any effect on preventing swelling. Usually storage additives just prevent gumming, and will often contain alcohol themselves!

    The swelling should be reversible to some extent, but that's not to say it will be easy. You could try removing the tank and letting it air, or put it in a bag with some silica gel or something - I expect someone's tried that already.

    In air, in a temperate climate, it should only swell by about 0.5%, so the whole alcohol / fuel / water situation must shift the equilibrium to the point that much more water ends up in the nylon. The swelling is said to be reversible, so this would indicate that air drying for at least a few days should help. Fuel drying additives tend to be alcohol based, which could just attract more water into the solution (effectively drying any air in the tank, or through the vent lines), which will then find its way into the nylon as well.

    https://techcenter.lanxess.com/scp/a...df?docId=76987
    https://techcenter.lanxess.com/scp/a...df?docId=76990


    I think not letting fuel sit for a long time in the tank could help prevent swelling in the first place. My rides out tend to be 100 or so miles, so I always fill up beforehand and it gets put away with whatever's left. Long term storage is a different matter, and if you can't guarantee the alcohol (or water) content of the fuel, it might be better to leave the tank only part-full if you don't fancy draining and removing it.
    2009 Shiver (White) | UK

  3. #3
    apriliaforum Member Ametts21's Avatar
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    Quote Originally Posted by IndelibleInk View Post
    As per:

    http://www.apriliaforum.com/forums/a.../t-241922.html

    The swelling is due to moisture getting into the plastic (polymer - usually nylon), which first clings to the alcohol content in the fuel, so the additive would have to be specifically formulated for it to have any effect on preventing swelling. Usually storage additives just prevent gumming, and will often contain alcohol themselves!

    The swelling should be reversible to some extent, but that's not to say it will be easy. You could try removing the tank and letting it air, or put it in a bag with some silica gel or something - I expect someone's tried that already.

    In air, in a temperate climate, it should only swell by about 0.5%, so the whole alcohol / fuel / water situation must shift the equilibrium to the point that much more water ends up in the nylon. The swelling is said to be reversible, so this would indicate that air drying for at least a few days should help. Fuel drying additives tend to be alcohol based, which could just attract more water into the solution (effectively drying any air in the tank, or through the vent lines), which will then find its way into the nylon as well.

    https://techcenter.lanxess.com/scp/a...df?docId=76987
    https://techcenter.lanxess.com/scp/a...df?docId=76990


    I think not letting fuel sit for a long time in the tank could help prevent swelling in the first place. My rides out tend to be 100 or so miles, so I always fill up beforehand and it gets put away with whatever's left. Long term storage is a different matter, and if you can't guarantee the alcohol (or water) content of the fuel, it might be better to leave the tank only part-full if you don't fancy draining and removing it.
    Wow what a great response, yeah I'm about the same as you do about 100 or 150 miles and whatever is left stays. But as the wether in North Carolina is too cold I will be letting her sit for the most part. Maybe I will just siphon out what I have in there and let it be. Just don't want to end up snapping mounting tabs on the fairings especially after I get them painted this winter, I also plan to check valves this winter so an empty tank wouldn't be a bad thing. I'm a process engineer and have done little bit of work with plastics including rotomolding which I would bet is how they create these tanks not sure as I haven't really looked at it but there's so many more advanced utilization of plastics and composites in today's industry's but aprilia...well whoever made the tanks for aprilia couldn't create the right process/additives to mitigate the swelling? Any who, I'm guessing the consensus is to drain the gas and let it sit like it is.

    When I first got the bike it had an issue with the check valve so every time I filled up I'd pull off the gas cap and the tank would expand because it wasn't replacing the fuel with air as it was used, after removing charcoal canister and such I fixed that problem which is what I originally assumed was the reason for the above mentioned problems but not the case.

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    I don't know if leaving the tank dry won't cause issues with the pump and lines if the residue gums up. Leaving a litre or two shouldn't be an issue, it's what I've done the last couple of years. Modern fuel is generally more stable, but it'll still e.g. clog a carb if you're careless.

    I have a process engineering "education", but don't really use it, so all this equilibrium nonsense is just tickling some vague memory for me
    2009 Shiver (White) | UK

  5. #5
    apriliaforum expert High Country's Avatar
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    At one point, I thought using StarTron additive would prevent swelling, since it is supposed to keep moisture dispersed in suspension. I used it religiously, and it didn't help.

    I remember reading about mixed results from letting the tank air dry in a warm location. If you're doing it on the bike, I'd run it dry (to prevent gas varnish), then loosen the mounting bolts just enough to give it room to shrink.

    They don't use ethanol in Europe, so Aprilia sees it as our mistake not theirs. I sure wish they'd used a different plastic though.
    2009 Aprilia Dosoduro 750 (Adventurized: http://www.apriliaforum.com/forums/a...893274&thumb=1)

  6. #6
    apriliaforum Member Ametts21's Avatar
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    Quote Originally Posted by High Country View Post
    At one point, I thought using StarTron additive would prevent swelling, since it is supposed to keep moisture dispersed in suspension. I used it religiously, and it didn't help.

    I remember reading about mixed results from letting the tank air dry in a warm location. If you're doing it on the bike, I'd run it dry (to prevent gas varnish), then loosen the mounting bolts just enough to give it room to shrink.

    They don't use ethanol in Europe, so Aprilia sees it as our mistake not theirs. I sure wish they'd used a different plastic though.
    Yeah i mean so can get ethanol free here but not with any type of regularity especially when were up in the mountains riding the good stuff we just take what we can get as long as it's 93. Mine has gotten worse, my ignition cylinder is touching the back of the ignition cover piece

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    In fairness, there shouldn't be any water in the tank in the first place. So deliberately adding hygroscopic substances to the fuel itself is pretty stupid when the effects of both alcohol and water are known to be detrimental to current fuel systems. Petrol / gas is one thing, alcohol is quite another thing - purely in chemistry terms. Of course, the alcohol allows fuel blends to "safely" contain more water before it even comes out of the pump, which saves on both production and feedstock costs - even before the water content, alcohol reduces your economy due to its lower energy content per volume.

    Water and alcohols dissolve in each other, to varying degrees, so the mixture is inherently "dispersed" - that does not mean it locks away the water, it is still physically and chemically active. The concentration is more consistent throughout the container, which can either help or hinder: e.g. dissolving the water like that means you don't get rust at the water / fuel interface on steel components, but it also means the whole tank is exposed to water, so no need to rely on the slow diffusion of water in the plastic to ruin your day - i.e. your tank is actually more likely to deform.


    They do use ethanol / alcohols in fuel here, especially in Diesel. We have E5 and E10, but the E10 has to be labeled as such with a warning it could harm your vehicle.

    Suddenly and drastically changing the operating conditions of materials asked to otherwise do the same job as before is all well and good for new bikes, but what about all the ones that have already been made and still need to use fuel? There are so many stories of modern fuel harming older cars and bikes, specifically related to alcohol (or its water absorbing tendencies). I suppose you could compare it to removing lead from fuel, and is to be accepted as part of "progress" - except the motivation is significantly different: removing lead "saved the planet"; adding alcohol can't yet, certainly not from corn.


    To effectively "hide" the alcohol content is dumb, though. Using fields to grow alcohol for fuel is even dumber - just make it from waste instead. But people do what is easiest and will make most money quickest.
    2009 Shiver (White) | UK

  8. #8
    apriliaforum expert Frodo's Avatar
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    As I understand it, ethanol added to normal gasoline reduces emissions and that this is partly due to the oxygen atom in the ethanol that gasoline does not have. It is also a cheap way of increasing octane rating without the addition of expensive and toxic petrochemicals. Sustainably produced ethanol reduces CO2 emissions, but many commercial crops producing ethanol for fuel are at best carbon neutral or actually be carbon positive (bad) due to the addition of synthetic fertilisers and fossil fuel powered tractors and increased emissions of nitrous oxide (from nitrogenous fertilisers). And I agree that it is dumb to grow crops for fuel when people are starving.

    I ran my Aprilia Pegaso Trail on an ethanol mix for 100,000 km. Seat of the pants felt that it ran better and the tank didn't swell one bit.

    Acerbis, which makes the tanks for Aprilia, should use a polymer that is not affected by water in ethanol mix fuels as this problem has been known about for a long time (see the Ducati Multistrada forums). I posted sometime ago that the tank in my new Shiver is made of polypropylene, not nylon, and that this is less sensitive to water. @Ammetts, what does the underside of your tank state in terms of the material used?
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  9. #9
    apriliaforum Member Ametts21's Avatar
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    Quote Originally Posted by Frodo View Post
    As I understand it, ethanol added to normal gasoline reduces emissions and that this is partly due to the oxygen atom in the ethanol that gasoline does not have. It is also a cheap way of increasing octane rating without the addition of expensive and toxic petrochemicals. Sustainably produced ethanol reduces CO2 emissions, but many commercial crops producing ethanol for fuel are at best carbon neutral or actually be carbon positive (bad) due to the addition of synthetic fertilisers and fossil fuel powered tractors and increased emissions of nitrous oxide (from nitrogenous fertilisers). And I agree that it is dumb to grow crops for fuel when people are starving.

    I ran my Aprilia Pegaso Trail on an ethanol mix for 100,000 km. Seat of the pants felt that it ran better and the tank didn't swell one bit.

    Acerbis, which makes the tanks for Aprilia, should use a polymer that is not affected by water in ethanol mix fuels as this problem has been known about for a long time (see the Ducati Multistrada forums). I posted sometime ago that the tank in my new Shiver is made of polypropylene, not nylon, and that this is less sensitive to water. @Ammetts, what does the underside of your tank state in terms of the material used?
    I am not sure I havent had the tank off yet, I will be doing valves soon so I'll check it out then. I'm thinking I'm going to drain the tank to let it sit empty during the winter

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    Quote Originally Posted by Frodo View Post
    As I understand it, ethanol added to normal gasoline reduces emissions and that this is partly due to the oxygen atom in the ethanol that gasoline does not have. It is also a cheap way of increasing octane rating without the addition of expensive and toxic petrochemicals. Sustainably produced ethanol reduces CO2 emissions, but many commercial crops producing ethanol for fuel are at best carbon neutral or actually be carbon positive (bad) due to the addition of synthetic fertilisers and fossil fuel powered tractors and increased emissions of nitrous oxide (from nitrogenous fertilisers). And I agree that it is dumb to grow crops for fuel when people are starving.

    I ran my Aprilia Pegaso Trail on an ethanol mix for 100,000 km. Seat of the pants felt that it ran better and the tank didn't swell one bit.

    Acerbis, which makes the tanks for Aprilia, should use a polymer that is not affected by water in ethanol mix fuels as this problem has been known about for a long time (see the Ducati Multistrada forums). I posted sometime ago that the tank in my new Shiver is made of polypropylene, not nylon, and that this is less sensitive to water. @Ammetts, what does the underside of your tank state in terms of the material used?
    Yep, petrol is full of nasty stuff like polyaromatic whathaveyous, before you even get into additives, so it makes sense to replace it with something cleaner. As long as we can make it cleanly, and from sensible feedstocks.

    Good to know that a PP tank option is in the wild at least!
    2009 Shiver (White) | UK

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    apriliaforum expert tubad56's Avatar
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    In an ideal world Aprilia would have made the tank a couple of ltrs bigger but why they didnt make it out of a more durable plastic is beyond me.
    My tank is that swollen that I try not to take it off (Air filter hasnt been changed in a while...18-24 months) its got to the point where it makes me think is it fit for purpose?
    2010 Factory DD that I want to make FACTORY Factory
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  12. #12
    apriliaforum Member Ametts21's Avatar
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    Mine needs to come off as I need to do valves and air filter....hopefully I can get it back on... kind of a shit design.

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    apriliaforum expert rule62's Avatar
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    Remove the 2 bolts that hold the rear subframe on each side. It makes lifting a swollen tank a non-issue.
    2014 DD 750 ABS - Spark exhaust, Arrow decat, headers (all ceramic coated), BMC filter, BikeMaster DLFP16-BS LiFePO battery, NGK iridium plugs, GPR steering damper, DD 1200 fully adjustable rear shock w/spring swap, 2016 Tuono Factory wheels, 15/44 520 conversion (PBR/Superlite/DID), Strada-7 fork preload adjusters, Samco 2-piece hose kit w/clamps, Engine Ice, Renazco Racing seat, EvoTech tidy tail, Aprilia grab handles, shorty levers, crank-case breather mod, evap-can delete... and a Rapid Bike EVO.

  14. #14
    apriliaforum Member Ametts21's Avatar
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    Quote Originally Posted by rule62 View Post
    Remove the 2 bolts that hold the rear subframe on each side. It makes lifting a swollen tank a non-issue.
    Great thanks! Subframe is getting powdercoat anyways

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    apriliaforum expert tubad56's Avatar
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    Cheers rule62 nice to know
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