Leaving bikes standing unused

How long does it take for fuel to go manky?

I ask because my gixxer has been laid up on the optimate for the past
few months due to a combination of crap weather, work commitments and
spending all my spare time trying to get my recently acquired Morini
running. Yesterday I got the irresistible urge to skive off work for a
few hours and go for a long blat but found that the bike is running
dog rough. The fuel light was on so I headed to the nearest petrol
station to fill up. No different with a tank full of fresh fuel, the
bike sounds like a tractor and coughs and splutters at low revs /
small throttle openings. On giving it beans it seems to clear itself
and hurtles forwards in the usual fashion. So, I gave the bike a good
thrashing to see if it cleared, but no joy. Still splutters at low
revs. What's up with it? I was thinking maybe the injectors are gummed
up, but then wouldn't that cause it to run rough right through the rev
range? I would have hoped it would take longer than a few months for
the fuel to turn to gunge.

Last time the bike was laid up for any length of time the alarm did
for the battery (hence the optimate). That time, on fitting a new
battery the red light stayed on with FI warning flashing (manual says
the bike will run in limp mode and to get it to the nearest dealer).
The dealer said the FI warning was caused by a sticking exhaust valve.
This was fixed under warranty and it has been fine since. This time
the battery was fully charged, the bike started first press and there
are no warning lights. But the bike certainly isn't running right.

Is it worth trying an injector cleaner fuel additive like redex or
similar? Or is this caused by something else?

 

It doesn't. It's a myth brought about by the deposits it can leave in
carbs if it's left to evaporate, particularly multiple times, which
can block up the jets etc.

--
_______
..'_/_|_\_'. Ace (brucedotrogers a.t rochedotcom)
\`\ | /`/ DS#8 BOTAFOT#3 SbS#2 UKRMMA#13 DFV#8 SKA#2 IBB#10
`\\ | //'
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I'd check the air filter first. There might be a spider's web, bird nest
etc that restricts air flow until you get a bit of pressure built up from
your forward momentum.

--
wessie at tesco dot net

BMW R1150GS

"Wessie is a lovely man with many wonderful qualities" TM Blaney

 

Hmmm..., having spent several hours stripping and ungumming the carbs
on the Morini I would say that fuel does, eventually, go manky.
However, it has to be said that the bike had been stood for years and
the previous keeper hadn't even drained the float bowls. The amount of
sludge had to be seen to be believed.

 

Good suggestion, ta. I'll send the Mrs in to check. Just in case the
spider is still in residence.

 

No myth. Fuel does indeed go 'off' over time. The volatile fractions
evaporate, and what's left is less than optimum. That said, since SimonM
has filled up a nearly empty tank with fresh fuel, this isn't his problem.
I'd advise him to run some quality fuel injector cleaner through the
system and see how it goes.

 

As Ace says, the problem isn't so much it going manky (though if left
long enough, the volatiles do evaporate, so he isn't quite right) as
fuel evaporating completely in carbs or injectors and leaving a gummy
deposit.

How long this takes is really a climate issue. I've left fuel for two or
three months in the UK, with no problems. Howedver, in a hot climate,
that's long enough for evaporation to occur and residues to form.

It is probably the most common bike problem of the era.

 

Sorry, that's not true. I've checked this out with specialist
chemists[1], and the fact is that at normal temperatures the various
components all evaporate at around the same rate. If the float bowls
have completely dried out, then clearly there may be some crap left
which may bung up the system, but the fuel in the tank should be just
as good as new.

The myth is often 'proved' when people flush their systems and fill up
with fresh, but of course this will also have the effect of cleaning
out the crap, which is what I believe then makes it run better.

Indeed.

[1] Well only one, my Sister-in-law, who used to be GM at a chemical
bottling plant.
--
_______
..'_/_|_\_'. Ace (brucedotrogers a.t rochedotcom)
\`\ | /`/ DS#8 BOTAFOT#3 SbS#2 UKRMMA#13 DFV#8 SKA#2 IBB#10
`\\ | //'
`\|/`
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<suspicious look>

Well it definitely has a different smell to it after a while - very
distinctive.

</suspicious look>

I don't know exactly how long the 'knacker your carbs' period is, but I
have been long past it (probably by years) on a couple of bikes, as I
know to my cost. I'm not sure what happens with FI systems.

 

I was told that petrol does not last very long at all since the
chemicals they used to add to it have all been banned, this may or may
not be true though..

Simon

 

For the last <fx:counts on fingers> 15 winters three different bikes,
all Kawasakis, all non-FI, have been laid up in the garage with nary a
glance for up to five months.

Without fail, each spring, apart from charging (or replacing) the
battery they have started up and run spot-on using the fuel left in the
tank.

I'm still of a mind that you would have to leave it for *yonks* to get
it to go 'bad', if at all.

 

It's only an issue if you're talking about reducig it's volume by a
massively noticeable amount. So if you leave a tank open for a year,
you'll quite possibly be left with gunge in the bottom, but if it's
sealed even as well as a normal fuel tank, it'll be years before that
happens.

--
_______
..'_/_|_\_'. Ace (brucedotrogers a.t rochedotcom)
\`\ | /`/ DS#8 BOTAFOT#3 SbS#2 UKRMMA#13 DFV#8 SKA#2 IBB#10
`\\ | //'
`\|/`
`

 

It takes a helluva long time for fuel in the tank to evaporate and go
off, but trust me, it does.

When I'm messing with SOBs, the one thing that makes me sigh and down
tools is that distinctive varnish smell from the carbs. On bikes that
have been standing for a really long time (like several years) you get
it from the tank as well.

 

Yes, indeed.

 

Well, it may be so that all fractions evaporate evenly, and not being a
chemist, I'll not make any more claims about that, but I'd be quite
surprised, even with my limited chemistry background, if that turned out
to be the case. In any event, there is also oxidation to consider,
according to the esteemed Mr. Adams:

http://www.straightdope.com/columns/060825.html

"The second cause of bad gas is oxidation–some of the hydrocarbons in the
fuel react with oxygen to produce new compounds, almost all of them worse
than what you started with. When oxidation becomes a problem, you'll know
it without lab tests--the gasoline gives off a sour odor."

No matter what the phyical basis behind it, it is well known that leaving
a bike (or any vehicle with a vented fuel tank) stand with fuel in it for
a matter of months, especially in warm weather, will result in nasty stuff
forming in the carburetors or various fuel injection gubbins.

I also like the rodent nest possibility, having seen plenty of evidence of
critters invading my garage, it's not unusual for them to pick an airbox
as a nice cosy nest to fill up with misc fluff and sunflower seed husks...

 

i.e. a common myth.

No, it needs a lot longer than 'a few months'. Only if the volume of
the petrol has reduced by, say, 30% or more (guessing, but YKWIM) is
it likely to become an issue.

--
_______
..'_/_|_\_'. Ace (brucedotrogers a.t rochedotcom)
\`\ | /`/ DS#8 BOTAFOT#3 SbS#2 UKRMMA#13 DFV#8 SKA#2 IBB#10
`\\ | //'
`\|/`
`

 

Not a myth at all- the more volatile bits will bugger off and leave the
shiter components behind if left for long enough. Been happening to
petrol for ages and the newer stuff doesn't seem much better for this
particular shortcoming.
--
Dave
GS850x2 XS650 SE6a

Teach a man to fish and he and his pikey mates will have the
river cleaned out in a day.

 

You'll get very little oxidation if the tank is kept full.

I think people storing bikes make the mistake of draining the tank as they
think the petrol will go off. This means that any petrol left within the
tank will most likely evaporate leaving a sludge, as it is subject to
heating & cooling as ambient temperature varies.

A full tank does not contain much oxygen but is also less likely to be
affected by ambient temperature variation. The full load of petrol will
also minimise corrosion from condensation.

--
wessie at tesco dot net

BMW R1150GS

"Wessie is a lovely man with many wonderful qualities" TM Blaney

 

I've got a strange one, and here is a tale too.

Years ago I rebuilt a Lotus Twin Cam that was completely wrecked
due to lack of use and being outside...
New everything, rebore, pistons ...
I think the head was cracked due to frost and was welded.

Finally - let's fire it up.

Nothing.

Had been suspicious of the fuel so changed that first,
no use, no go. After some hours of headscratching
changed the plugs for another new set. Fixed.

Presume that the old fuel had wrecked the new plugs.
They looked OK, brand new and completely unused in fact.

No clue as to any possible mechanism.

I seem to recall that the fuel seemed a lot darker than would
be expected.

 

Read the rest of the thread. Or in short: No, it doesn't. It's a myth.

--
_______
..'_/_|_\_'. Ace (brucedotrogers a.t rochedotcom)
\`\ | /`/ DS#8 BOTAFOT#3 SbS#2 UKRMMA#13 DFV#8 SKA#2 IBB#10
`\\ | //'
`\|/`
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