Plastic Tank problems: Discussion thread, see info thread sticky for updates

[herm]

OR/NH/ME
always garaged
ridden in all kinds of weather

i think there is a direct connection between how often the bike is ridden (how often fuel sits in the tank) and the severity of the expansion problem.

up until recently i was cycling a tank of fuel almost every day. never had any signs of expansion. but in the last year (as my riding time has diminished) i have started to see some of the signs.

maybe i misunderstand the problem, but this makes sense to me since the fuel is not sitting in the tank long enough to cause mischief.

[xcaptainxbloodx]

I saw a bike that had sat on the showroom since new get a new tank.

[DRKWNG]

My SC has always been garage kept, both here in DC and in HI before.

[Mojo S2R]

NY Garaged  Never seen rain

How many tanks changed?

OR/NH/ME
always garaged
ridden in all kinds of weather

How many tanks changed?

My SC has always been garage kept, both here in DC and in HI before.

Same question?

[JimmyTheDriver]

Just to chime in,

I purchased a 2007 S4R this spring with 4 miles on it.... talk about leftover inventory.

Anyway, it showed major signs of deformation on the tank while sitting on the showroom floor.  So much so that I got them to discount the bike because of the tank, which they later replaced before I even took delivery of the bike.  

Since delivery (with the new tank) I have ridden the bike 3.5k miles, which is at least a couple times a week with a long one or two on the weekends.  Always filled with Northern VA (10% ethanol) 93 octane gas.  The bike is kept in a detached, non-climate controlled garage and the second tank is already showing major signs of deformation.  Ripples, shifting off the bumpers, can hardly unclip it anymore.

So that puts me at needing a third tank in 6 months of ownership.  The first deformed on showroom floor over three years of sitting.  The second deformed over a couple months in a steamy garage over the summer.

-Jimmy

Edit: To the point below my post, it's extremely humid in Northern VA in the summer.

[ducatiz]

I have to ask:

Are the people who are having their tanks replaced, are your bikes garaged, or out in the elements, or ridden in the foul weather on a regular basis?

I wonder if people who have garaged bikes, that never ride in foul weather, are less likely to have a tank expand, than someone who has their bike sitting outside all year round.

Also, how many people from dry climates, like Arizona, New Mexico, Colorado, and Nevada are needing to have their tanks replaced, vs people from wet areas, like NY, Michigan, New Hampshire, and Washington?

It's a reasonable assumption that bikes from drier climates will have less replacements needed.

I don't think rain is an issue at all. 

Ethanol wicks moisture from the air.  The easy way to demostrate this is to put some pump gas into a small bottle -- like a liter soda bottle.  Let it sit open in a safe place, like your garage on a high shelf or some place it can't be easily knocked over.  After about 60 days, the ethanol will begin to separate. 

This is the separation with about half a liter of gasoline . I used pump 87 octane from Sunoco, 10% ethanol.  It sat for about 40 days.  It is hard to see in this pic, but the reddish part at the bottom is the ethanol and right on top it is about 1mm of clear fluid--pure water.

[arai_speed]

My 2007 S4RS sits in an enclosed garage for most of the week.  She's fair weather weekend queen and mostly sees canyon roads.  89 octane, 10% ethanol is what I use.  I live on Los Angeles CA.

I went in for my 3rd tank this past weekend.

[ducatiz]

Wow

[ducatiz]

I forget, do you have the original?

Call ducati cust svc?

[DRKWNG]

How many tanks changed?
How many tanks changed?
Same question?

My SC currently has its third tank on it, and it is showing signs of deformation.

[sbrguy]

wow so that is what it looks like with the ethanol separating with the water.  

but if that takes something like a few weeks to separate like that, if the gas is constantly shaken, ie you ride the bike it shouldnt separate?  but apparaently it doesn't matter and still does separate out to deform the tanks. strange.

for the older monster tanks it looks like that company out in japan with the alum tanks should be picking up business, yes they are expensive but to not have to deal with the tanks expanding anymore and the hassle may be worth it to some people.

i'm surprised the market for used FI metal tanks is not crazy good for sellers with the people of the older style monsters with plastic tanks.

[ducatiz]

Shaking it doesn't remix.  The ethanol/water just sinks again.

My point also that you have no idea what condition the fuel tanks at your station are in, or how often they get refilled

[Meerkat]

wow so that is what it looks like with the ethanol separating with the water.  

but if that takes something like a few weeks to separate like that, if the gas is constantly shaken, ie you ride the bike it shouldnt separate?  but apparaently it doesn't matter and still does separate out to deform the tanks. strange.

for the older monster tanks it looks like that company out in japan with the alum tanks should be picking up business, yes they are expensive but to not have to deal with the tanks expanding anymore and the hassle may be worth it to some people.

i'm surprised the market for used FI metal tanks is not crazy good for sellers with the people of the older style monsters with plastic tanks.

Turns out that the water doesn't have to separate to be absorbed by the plastic tank. Just the fact that the ethanol is present is enough to increase the rate at which the water is absorbed by the plastic.

You can think of this as a chemistry problem with multiple equilibria:

H₂O(air)  ><  ethanol/gas mixture  ><  PA6   (where >< is equilibrium arrows)

If you look at the equilibrium between the H₂O(air) and the ethanol/gas mixture, there is a partition coefficient which describes how much water dissolves in the ethanol/gas mixture. This is much higher than the amount of water that dissolves in pure gas (this is why ethanol free gas causes less of a problem). There is a similar equilibrium between the "wet" ethanol/gas mixture and the PA6. When the water enters the plastic, the material swells like a dry sponge that is wetted for the first time. The polyamide 6 (PA6) has lots of amides (as one would expect from its name) which can hydrogen bond with the water, which is why it absorbs it.

My chemistry phd tells me that this is a really shitty material for use in a critical place like fuel tanks, particularly given the desire of the feds to increase the ethanol content. Although I'm not a chem engineer, I think it's likely that the polymer properties are drastically different after exposure to h2o EVEN IF you "dry" it out and it "shrinks back" to its original size. The other thing that I think many people overlook is that the swelling is a 3-D process: you think your tank is bigger because it looks bigger on the outside, but the plastic is really just thicker. So I'd bet many of these tanks don't hold as much gas as they did when they were new and unswollen.

Just my 2cents!

[CDawg]

...you think your tank is bigger because it looks bigger on the outside, but the plastic is really just thicker. So I'd bet many of these tanks don't hold as much gas as they did when they were new and unswollen.

There goes my silver lining.

[Bladecutter]

I hate to ask the obvious, but if your bike is going to sit a while, can you just drain the gas into a container, wait for the ethanol to separate, and then pour the ethanol free gas back into the tank, potentially eliminating the issue?

Then again, if you're going to go through all of that, you might as well just leave the tank empty, since its not going to rust internally like a metal tank might.

Sounds like it might be something to do for those who's bikes sit for winter storage, waiting for repair parts, or for any real amount of time? Might help reduce it, even a little bit.

BC.