Long term storage

[Atabeach]

Gentlemen, I only have one arse…I have 4 bikes and was considering laying up my rarely used 1994 k75S with 7000 miles. Should I empty tank? …or fill with non ethanol and leave be? I don’t want the fabled tank leak….TIA

[Laitch]

How long is "long term"?

[Atabeach]

A year or longer…I have another k75S. My daily driver.

[The Mighty Gryphon]

I would drain the tank completely and dry it thoroughly down in the low points where water would collect.  With the tank totally dry you have the option of refilling it with non-ethanol gas mixed with Stabil and Techron, running it for a minute or two to circulate the new fuel through the system and then leaving it alone OR just closing the cap on a nice dry tank.

If you do opt for the dry tank, you might want to add Techron to the fuel in the tank and running the engine to circulate it through the system before you drain it.  That is to prevent the fuel from gumming up the injectors during the idle period. 

[Atabeach]

Thanks Griff he main concern here is the tank leak. From what you are telling me....Non ethanol gas will not corrode tank?  Generally speaking?....

[Chaos]

It's not so much ethanol or not, it's water that collects at the bottom of the tank that causes the corrosion. (water is heavier than gasoline)

[The Mighty Gryphon]

It's not so much ethanol or not, it's water that collects at the bottom of the tank that causes the corrosion. (water is heavier than gasoline)

That's why you want to drain and dry the tank.

[daveson]

Over here in Oz where lower standards are accepted and the fuel has higher sulphur levels, I have some bricks. The K75 never had ethanol blended fuel by the previous owner, my blue one did. Ethanol absorbs water, so water didn't accumulate at the bottom of the tank of bluey, and the tank of bluey is in good shape. The K75 was leaking at both low points.

Although ethanol absorbs water, it also attracts it. The fuel sender in bluey was totally covered with rust, but in the K75 it was spotless. When water combines with sulphur, you get sulphuric acid, not good. Condensation accumulates over time, so I guess it's good to use ethanol at least once a year. So the idea of draining the fuel and putting fresh fuel in, I also think is good. Fuel will stop the pump seals from potentially drying out, so storing the tank empty would be better, with the pump removed and stored in fuel. A full tank of fuel means less surface area inside the tank where condensation can occur.

One year in storage isn't much to worry about.

That's just the way I think about it.

[The Mighty Gryphon]

The main problem is phase separation when the ethanol absorbs more than .03% of water from the atmosphere.  At that concentration, the water and ethanol separate from the fuel and collect in the low points of the tank where it becomes a medium for breeding bacteria.

The unfortunate fact is that this mixture is more corrosive than the water alone.  Also, as the corrosion process proceeds, the mixture becomes more conductive allowing for electrolytic corrosion between the aluminum and other metals in the tank. 

The distilled water that would collect in an empty tank due to condensation is far less corrosive to aluminum than this nasty mix. 

For short term storage of a year or less in a moderately dry environment corrosion shouldn't be that much of a problem.  As humidity increases, the corrosion danger increases as well.  Still, over a long term, even a relatively dry environment could allow damage. 

Bottom line is that if you are sure the fuel wouldn't sit in the tank for more than a year you are probably okay.  The problem comes when a year turns into 2 or more years of neglect.  Even the stabilizers that are designed to prevent phase separation only claim to work for periods up to one year.