how long for dry tank to shrink back?

[BK_856er]

I had two warranty tanks due to expansion.  Current one has now swelled to the point where lifting the tank takes tools, but it's off, fuel pump is out and it's bone dry after putting a fan through it all night.  I've heard that the tanks will eventually shrink back to their regular size if dry.  How long does this take and are there known methods to accelerate the process?  Given the mass of the material and the fact that it takes a couple years to swell up, this has go to take a while, right?

BK

[Bill in OKC]

My house has heating vents in the floor.  After it has dried enough that the fumes are minimal (thank you EPA) I set it near a vent so warm air blows through it over the winter months.  I don't know exactly how long it takes but after a couple of months it seems normal - it never has gotten as bad as yours to start with though.  Warm dry air speeds up the process.  I think a month or two of just regular drying would do it.

[BK_856er]

That's genius using your forced air heating.  I don't have that option, but I strung the tank up in the garage with a fan blowing into it.  I've also taken measurements, so I'll see how it goes, and if it shrinks enough before I get impatient I'll coat the interior.

BK

[oldndumb]

I have no experience with the plastic tanks so bear with me if I ask a stupid question.

What is the determining factor as to when a "dried" tank is ready for coating?  

Measurements, as mentioned by the OP seem logical, but who would have starting dimensions to refer to?  Or do you keep measuring until the dimensions stay the same? Or, maybe stop the drying when the tank fits properly? Or when the snow melts?  

[BK_856er]

The plastic (nylon) tanks swell over time when used with ethanol containing fuel.

Some reports indicate that when stored dry (no fuel, on the shelf) they will shrink back to their former dimensions on the ~months timescale.

Ducati used to warranty these swollen tanks, but that ended a few years ago with a class action lawsuit.  Some owners apply internal coatings to new or cleaned/non-swollen tanks to avoid the shape change.

Swelling/expansion can cause poor fit on the frame and interference with the ignition cylinder and a bloated look.  I'd say up to ~0.5" increase in all directions.  I simply defined some reference points on my own tank and will try to monitor dimensional changes over time.  When it fits well I will coat the interior, unless I get impatient and just decide to reinstall again.  Probably the latter!

BK

[jerryz]

I have seen a M695 tank in UK stretch 1'' in all directions and  take up ll the space to the ignition switch .

[OrangeDragon]

I was able to buy a new plastic tank off of eBay.   I measured across the tank to the screw holes where the rubber mounts are attached.

New tank: from center line to center line of screw holes, it measured 11 3/8"
Swollen tank: from center line to center line of screw holes, it measured 11 3/4"

after three months, the old tank had not shrunk to match the measurements of the new tank.  i stopped checking after that and put the tank in storage about 6 months ago.  when and if it shrinks back, i will apply the caswell coating

i coated the new tank with caswell and hasn't expanded at all.  The only con to the coating was losing a bit of fuel capacity.

if you plan on coating, i recommend using one of the colored coatings so it will be easy to see what has and hasn't been coated.

[ducatiz]

if the tank is dry, remove the fuel pump plate and stick a small hair dryer inside it on cool and let it sit.

this time of year is a good time to do it because houses are dry from the heating.

i would rinse the tank out first -- use water based marine clean.  rinse rinse rinse.  you need to get the gasoline out.  you'll need to rinse it again later with xylene.  some people have used acetone but it does attack the nylon.  xylene is compatible with nylon and can be used to cut the coating.

[BK_856er]

That's great info mr. dragon.  I'll pull my frame bumpers off and compare the distance.

I take it your unproductive 3 months were static on a shelf?  I washed out my fuel residue with dish soap + water and then rigged up a "vornado" fan on full power blowing into the fuel pump opening and exiting the fuel fill hole with quite a force.  I'm hoping that over time the constant air flow accelerates the shrinkage, though I'm not expecting miracles!

BK

[ducatiz]

soap probably works ok, but i would use a stronger solvent like marine clean or purple (diluted).

it takes 2-3 months in a dry place for it to dry out and shrink.  it is water and some alcohol that you're venting out.

[OrangeDragon]

I used marine clean to wash out my old tank.  For first three months of drying, the tank was out in the open on the floor where it was exposed to daylight during summer months.  the air is typically dry out here in California.  I did not attempt to accelerate the drying process with fans etc.  Basically, I was not in a rush since I had a brand new coated tank to install and figured a slow gradual shrinking process for the old one would be better than the accelerated route.  I have since placed the old tank in the original ducati box the new tank came in and put it in storage.  So this current storage set up might not help the shrinking process.

I should have noted that during the three months the tank was out in the open, it did shrink but not to the 11 3/8" to match the new tank.  It seemed to stay a little over 11 1/2" from center to center screw holes for a long time. 

Also, when my second tank expanded the ducati dealer swapped out the original rubber mounts with some larger rubber mounts that can be adjusted because there are some slots.  I can tell the new tank hasn't expanded because they are where I initially placed them. 

[xcaptainxbloodx]

Aprilia never replaced their affected tanks. Their instructions were to remove the tank and let it sit for 4-6 months to allow it to come back to shape, I would assume a similar time frame for ours.

[itsamonster]

Wish i'd thought of doing this over the winter months. I've ordered an ally tank from Beater in japan at massive cost!  Doh!

[BK_856er]

Wish I'd thought of this before taking basically 2yrs off of riding!   

BK

[Bill in OKC]

Wish i'd thought of doing this over the winter months. I've ordered an ally tank from Beater in japan at massive cost!  Doh!

Doh!  Now you've gone and done it...  I searched Beater Japan and found they make an alloy tank for the S4Rs - oval fuel pump and all.  More stuff to spend my money on 

http://japan.webike.net/products/21788539.html