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Thread: Fuel tank breather 1125r

  1. #1
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    Fuel tank breather 1125r

    Hi there,
    Just wondering if anyone has successfully stopped their fuel tank breather dripping fuel out & if so how?
    I've tried secondary filter breathers to atmosphere which eventually soak & drip.
    I'm now making a small charcoal drip tank that I can empty when necessary, it also vents to atmosphere & I may fit a filter breather on the end as well. Just finished it so no results as yet but hoping it will work.
    Anyone else done anything different that has worked or is a work in progress?
    Thanks folks.

  2. #2
    Senior Member 34nineteen's Avatar
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    Quote Originally Posted by paul.berry View Post
    Hi there,
    Just wondering if anyone has successfully stopped their fuel tank breather dripping fuel out & if so how?
    I've tried secondary filter breathers to atmosphere which eventually soak & drip.
    I'm now making a small charcoal drip tank that I can empty when necessary, it also vents to atmosphere & I may fit a filter breather on the end as well. Just finished it so no results as yet but hoping it will work.
    Anyone else done anything different that has worked or is a work in progress?
    Thanks folks.
    So, you're making a breather to fit a tank that is receiving fuel from another breather from another tank?

  3. #3
    Senior Member Cooter's Avatar
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    He's making a reservoir for fuel vapor, silly.

    IMO, I'd let it drip. Or put it on a rear stand. That stock vent is only open when the bike is on the side stand.

    If you can't deal with that, use the charcoal can set-up you already have... and put a hose from it to a 'ported' vacuum source at the TB. It will empty the fuel vapors from your charcoal can for you. No more draining.

  4. #4
    Senior Member 34nineteen's Avatar
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    I would add one more catch tank and breather for good measure.

  5. #5
    Senior Member Cooter's Avatar
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    Like Christmas lights, just hang them all around the bike!

  6. #6
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    Quote Originally Posted by Cooter View Post
    He's making a reservoir for fuel vapor, silly.

    IMO, I'd let it drip. Or put it on a rear stand. That stock vent is only open when the bike is on the side stand.

    If you can't deal with that, use the charcoal can set-up you already have... and put a hose from it to a 'ported' vacuum source at the TB. It will empty the fuel vapors from your charcoal can for you. No more draining.
    Sorry but it doesn't make sense that the vent is only open on the side stand, how does the tank vent when the bikes running if that's the case?
    I can deal with drips, just not under the rear wheel when I'm trail braking & hard left cornering, which is the reason for the vapour trap & for my doubt about the vent only being open on the side stand.
    I don't fit stuff on my 1125r for the sake of it, the charcoal trap is a tiny 3" by 1" alloy container that fits under the seat, one pipe in & one out. It certainly isn't bling & weighs in at 10 grams with charcoal.
    Thanks for the reply Cooter.

  7. #7
    Senior Member 34nineteen's Avatar
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    The vent tube should exit at your passenger peg mount, if I'm not mistaken (my 1125CR's did that).

    If you are venting enough raw gasoline to cause a safety issue while riding, you have a much bigger problem. Do you have the insulation on the inside of the frame rail?

    Even when I got my 1125's super hot to the point where I was boiling fuel in the tank, I would only get a few drips when I would shut it off and let it heat soak.

  8. #8
    Senior Member Cooter's Avatar
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    The breather on your bike that leaks fuel now is for relieving pressure build-up in the tank. That overflow should NOT be dripping while under throttle, only after you shut the bike off, put it on the side stand, then it's doing it's job. 1125's are notorious for freaking people out. Gas is flammable ya know LOL.

    There is a different valve in the gas cap that will bring in fresh air to replace the gas you're using while the bike is running.

    Trailbraking is NOT done with the rear brake, unless you enjoy epic high sides... and a couple drips won't matter either Mr. Rossi

    I "think" it's in this video, if not its in one of the NCCR workshop vids, find it yourself for proof if you wish...
    https://www.youtube.com/watch?v=DuHWLUIUiiA&t=945s

  9. #9
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    Quote Originally Posted by 34nineteen View Post
    The vent tube should exit at your passenger peg mount, if I'm not mistaken (my 1125CR's did that).

    If you are venting enough raw gasoline to cause a safety issue while riding, you have a much bigger problem. Do you have the insulation on the inside of the frame rail?

    Even when I got my 1125's super hot to the point where I was boiling fuel in the tank, I would only get a few drips when I would shut it off and let it heat soak.
    Hi 34nineteen,
    I have 2 1125r's both are insulated with an extra fan, both tuned ECUs, airboxes, stacks & exhausts, both run under 87 degrees all the time & both have the venting problem.
    I use one of them at Santa Pod & the fuel drip is a particular issue for this.
    The problem seems to be that everyone thinks they only drip when they're hot & parked, in reality that's the only time I see it but they are venting all the time especially when hot & when the fuel is being tossed around in the frame whilst riding.
    The vent tube standard does exit at the left foot peg which explains why the fuel ends up under the rear tyre.
    Don't get me wrong here, it isn't pissing out, it's just the odd drip or splatter but enough to lose grip, especially on spirited down hill lefties.
    I just wondered if anyone had successfully dealt with this issue but seems people don't have an issue with it.
    Anyway, I'm hoping this little charcoal laden canister (third serious attempt at dealing with this) will soak up any gas for the time being & may give me an indication of just how much actually leaks during a ride.
    Can keep folks informed if you want?
    Otherwise thanks for your reply. You take care now.

  10. #10
    Senior Member 34nineteen's Avatar
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    Is the fuel boiling?
    Are you overfilling the fuel tank?
    Have you checked the operation of the fuel tank vent valve?
    Is the bike overheating?

    Any container of hot fuel is going to build pressure and need a place to vent that pressure to. Why not just reroute the vent house further back on the bike so any drops that are expelled are left behind you? Or just do your elaborate system of charcoal filters and catch cans. After all of the mods you said you have done to the bike; this should be easy.

    Have you actually measured the amount of fuel leaking from the hose while riding or just making an assumption? How hard are you leaning this in the turns where a drop of gas is enough to spell certain doom?


    Last edited by 34nineteen; 09-16-2020 at 03:46 AM.

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