*old* fuel

[jonbuoy]

I've had hassels with blockages after only a few weeks -seems to turn to syrup in the float bowls. I've found the same leaving a dish of petrol to evaporate - petrol goes leaving a pink oily residue.

[bart]

My DRZ only lasts about 2 weeks before I have to drain the carb. I've learnt to have a 14mm spanner handy.

Bloody thing. I've left other bikes for months without problems.

[Mike748]

If the bike has been sitting outside for a few weeks it could easily be a case of moisture that has got into places it shouldn't have, or a MSTRS said the fuel in the float bowls has evaporated, most possible and if the carbs haven't been apart for a long time any sediment that has been sitting in the bottom of the bowls could have easily been sucked into the jets of the carbs that are fluffing around.

The fuel wont have gone stale after that amount of time, a good example is a bike I've been sorting out at work; a 87 GSX750SF Katana that had been sitting in a shed for 3yrs.
Ripped the battery out as it had calcified 3 cells, hooked up a fresh battery, drained the float bowls (the remnants of fuel that came out was GREEN) primed the carbs with the fuel that was still in the tank (smelt off), switched her on, opened up the choke & hit the starter button, the engine spun over a few times then caught on 2 pots then 3 & finally all 4 and sat at a steady 3500rpm slowly eased off the choke and it sat idling (slightly rough but still idling).

Agreed, had to use jumperleads to start a bike that had been sitting in a shed for three years, it took a bit of cranking as there were other ignition issues, but it fired up proving it could still run.

[sels1]

My last bike was parked up for several months before I bought it and I had intermittent problems for a few weeks - had the carb cleaned and some additive added to some fresh petrol, and a few good long runs and the problem went away.
Affects some more than others but yes, fuel can go 'off'

[koba]

Its not so much separation as evaporation. Some of the additives in 96 are particularly volatile - ie Toluene - and evaporate more quickly. So it goes from 96 to more like 91. Some motors wont notice this, others will.

Correct on the evaporation but not quite right ( I think, I'm not an expert Ive just finished reading a good book)
toluene (tolul or methyl benzine) in fuel is likely to be part of what is left.
Fuel is a big mix (see above)of up to a hundred components and the components of the mix do evaporate at different temperatures, some very low, some much higher.
The stuff with the low evaporation point is the stuff that cooks off first, it is also the most volatile part of the fuel, useful in......Starting! the octane is most likley Raised by sitting around as the faster burning more volataile components evaporate off BUT octane is not the sole determining factor in a fuels performance so it aint nessecaraly good fuel!
To add to this fuel companies constantly vary the mix based on availabiliy of components, climactal and seasonal requirement etc, apparenty it is changed as often as monthly.
With a huge temperature change in the last 6 weeks it is also likely that what is left of the orignal fuel blend is no longer apporpriate for the current conditions, adding some ether based spary like "start ya bastard" give the motor a shot of more volatile fuel, thus helping it get cranked up enuf to burn the "off" fuel in the tank.

My crap fuel generally ends up in my veedub, they can run on some shocking fuel so im sure jim.cox is correct about different motors.

[koba]

My DRZ only lasts about 2 weeks before I have to drain the carb. I've learnt to have a 14mm spanner handy.

Bloody thing. I've left other bikes for months without problems.

Curse of the single!
Always such a bastard to start, luck ya don't have to do it on rollers... Try ether.

[Katman]

The small amount of fuel in the carb bowl will go off a lot faster than a large amount in the tank.

[sinfull]

Way i heard it is that petrol companies are adding crap to make feul go off quicker, to stop stock piling of cheaper gas !
Have had a few vintage cars stored in the garage and never had problems, but these days even the weedeater is a shit to start and runs like my nana, if the gas has been sittin in the can for a few months !

[bart]

I use the same fuel in my lawnmower as the DRZ, and it starts first pull after a couple of months of sitting. Might be the combination of electric start and shit fuel. I only use the red stuff (96 octane).

[lb99]

this bike was started on fresh fuel, but ran fine on the fuel that was in the tank,(because I forgot to fill it with fresh stuff) hadn't been registered/used for 13 years

[Grub]

One of the likely scenarios is water in the fuel. MSTRS mentioned that but the cause is not necessarily a "leak" into the tank.

Condensation in a fuel tank is a major safety issue with aircraft. It never forms in full tanks but it is a real threat if the tanks are below half full. It is part of every pre-flight check to drain some fuel and check for water contamination.

If your tank was low and the weather has got icy cold over the last few weeks then water in fuel is a real possibilty. If course it's heavier than fuel so it will sink to the bottom of the tank. To check, all you have to do is switch to reserve (if you have that) and drain about 50cc into a clear container. You'll soon see the water in the bottom with fuel on top.

[Katman]

Water in the bowl isn't likely to be the problem unless the bowl was full of water - and then the bike wouldn't run at all. Water sits at the bottom of the bowl and is only sucked into the jet when the fuel in the bowl has been agitated or at full throttle.

[FruitLooPs]

Friends ZXR250 that had been sitting did the same thing, flat battery and wouldnt start with pushing. It'd turn over and occassionally pop, I got worn out with pushing the bloody thing in the end, and we got one huge backfire with blue flame out of it

Eventually a few more pushes and it started, rough as hell gave it a bit of stick and it went but was pretty poor. Dumped the gas in the tank and it was horrible brown lookin stuff, fresh stuff in give it a run and bobs ya uncle.

[FROSTY:Me]

of course its NOTHING to do with the bike having a suspect battery -low voltage not enuff spark. making for fouled plug making for shit running.
Prove me wrong. Connect up a jumper battery and see how she fires up.
Betcha the deterioration aint in the fuel after 8 weeks --its in the Battery

[awayatc]

before a trip away i always close my fueltap and leave bike running untill it dies .....
It always starts first go whenever I get back....stale fuel never been an issue, and I hav been away for 3 month trips regularly....