Water In Tank

Discussion in 'Technical Help' started by Lautrec, Oct 26, 2023.

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  1. Lautrec

    Lautrec New Member

    Mar 1, 2023
    2
    3
    UK
    What are the ways water can get into a fuel tank?

    I ride a Street Twin, it has had issues since I got it but today was very apparent. I left the house this morning without incident, but shortly after there was a torrential downpour of rain that lasted several hours while parked. When I went back to my bike, it started but then barely ran - sputtering, stalling, backfiring/popping, very rough running, erratic idle and throttle response.

    I have had this issue before last year and had it in with the mechanics, they found water in my tank. I have since replaced the fuel cap, and it seems to make a good seal. There was no water that I saw when taking it off. I cannot see any damage on the tank. I can't see any damaged/cracked hoses. I ran a wire down the hole near the top of the fill port, but I don't understand how that hole works.

    I am very confused as to what is causing the problem and would appreciate any help offered. It runs generally fine again after 5-10mins of riding.
     
  2. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,495
    750
    Birmingham
    I assume the hole by the filler is a breather. If the cap is fitting properly maybe the water is from the fuel itself. Are you using E10 and is the bike in regular use, the E10 contains 10 pc ethanol which absorbs water which sinks to the bottom of your tank.
    Try a different fuel station.
     
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  3. Pegscraper

    Pegscraper Elite Member

    Jun 12, 2020
    3,011
    800
    Yorkshire
    If water was getting into the tank that easily, fuel would be getting out just as easily IMO and you would smell it.
     
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  4. littleade

    littleade The only sane one here
    Subscriber

    Mar 17, 2015
    255
    1,000
    Worcestershire
    Are you sure it's water in the tank again? It might be a HT problem so I'd check the plugs, plug caps and leads to see if they're breaking down when wet.
     
  5. Lautrec

    Lautrec New Member

    Mar 1, 2023
    2
    3
    UK
    I'm not certain yet, I have ordered a little pump to drain the tank (I'm not confident enough to take the tank off and drain it that way). I am just going on an assumption of what happened last time, and that it rained so heavily while parked and it was fine that morning you know.

    The sparks seem OK, I didn't see any arcing and they look in good condition. Every time I've had it in for maintenance/repair they've come back to say the sparks are OK.
     
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  6. Lautrec

    Lautrec New Member

    Mar 1, 2023
    2
    3
    UK
    That's what I thought too, surely if the tank is leaking THAT much that this much water could get in (it still runs terribly days later now), surely I would smell fuel or be leaking it.
     
  7. Lautrec

    Lautrec New Member

    Mar 1, 2023
    2
    3
    UK
    Yeah I think it is a breather. I've looked at the cap meticulously, I can't see how it would leak that badly you know.

    I've got E0 in it at the moment, but it's possible that it's the fuel station, I've considered it. I filled up my tank maybe 4 days beforehand - is it possible that the issue is just less pronounced with a full tank? As in, the fuel to water ratio was higher so was OK, but now that I've dipped lower the water is more of a problem? Bike is used practically every day, I generally use the same fuel station as it's in a convenient location, but in the past the issue has manifested soon after filling up. I remember thinking at the time, what a coincidence.
     
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  8. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,495
    750
    Birmingham
    Well first off I would try fuel from elsewhere and E5 not E10.
    I see you have also been advised it could be ht cables which is certainly true, i just answered your original question. Have you tried spraying the leads and caps with wd40 to displace any water ?
     
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  9. Baza

    Baza Elite Member

    Jul 25, 2020
    2,627
    750
    Home of Amazing Grace
    I would tend to go the electrical route as well.

    If you have water in your tank it will probably have got there by condensation on the exposed sides of a partially filled tank. Even if you do have water in the tank it will be very little and at the very bottom of the tank, nowhere near the fuel intake to the pump.

    The fact that the bike runs fine after 10 minutes of riding suggest that the heat of the engine is dissipating the moisture in the electrics that is causing the problem.
     
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  10. Lautrec

    Lautrec New Member

    Mar 1, 2023
    2
    3
    UK
    Thanks for your replies, I appreciate it.

    I have tried something a little...unconventional. As last time I had water in the tank, I have put a hole in one side of a re-sealable plastic bag and pushed my tank cap through it, so it's fully covered and sitting against the lip of the fill port. The bag fully covers the cap and surrounding area.

    I have had no issues since even though I've had the bike absolutely soaked with rain, and it's actually running better than ever before. I am going to keep the bag on for now to see if the issue returns, but it seems like my cap just has a leak - I really still don't know how.

    Is it possible that a leaky cap can also impact performance due to the EVAP system? I've noticed that my idle revs are much much stronger and I no longer have them dip stupidly low when pulling the clutch coming to a stop.

    What would be the best way to improve the tank seal? I've already replaced the cap once, but I suppose it's still not sealing properly.
     
  11. MoreT

    MoreT Senior Member

    Jun 12, 2022
    293
    113
    Hampshire
    Interesting topic, I always use E5 though I put E10 in the car. That's just because I love the bike more.

    Not too a serious a note: give it a good shake as some people swear by a little water injection to improve combustion. It's long been known to work if the water is pre-split into Brownian gas (Hy and Ox).
     
  12. MoreT

    MoreT Senior Member

    Jun 12, 2022
    293
    113
    Hampshire
    Recently I was researching alcohol as I use ethanol for heating at home.
    However I came across the use of isopropyl alcohol to dry out water from the tank. It has to be 99% and no more than 1/2 to 1 pint per full tank depending on how much water you have there.

    Do your own research though before doing it.

    My understanding is that you can then just run the engine as normal to burn off the alcohol as fuel. Best to make it a long run though and empty the tank, then fill up with good fuel afterwards so as not to damage any plastics. The forum I found this on was for outboard marine motors.
     
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  13. timboo

    timboo Senior Member

    Oct 17, 2021
    275
    113
    Cambridgeshire
  14. Iron

    Iron Elite Member

    Dec 29, 2021
    2,571
    943
    Bob Ross Studios
    Try one of these. I bought one and was amazed that they actually work. Pour the fuel through it, water (and anything else) stays left behind in the bowl.

    https://www.see-marine.co.uk/fuel-funnel-filters/f1-mr-funnel-fuel-filter-and-water-separator

    I think I got mine off Amazionian rather than the above. Bit more expensive but at least they have them.

    https://www.amazon.co.uk/Hopkins-F1NC-FloTool-Non-Conductive-Filter/dp/B00N4UN1RM/ref=sr_1_17?crid=331OLVUIJ1CHI&keywords=fuel+water+separator&qid=1701553083&sprefix=fuel+water+,aps,64&sr=8-17
     
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