b1h fuel tank vent

robertw95 · Trackday Trickster Joined: 22 Nov 2014 Karma :

Ok so my trackbike has a problem with the tank vent.There is a vacuum being built up inside tank causing fuel not to go through leaving me with a huge flatspot and surging. I replaced the cap with a quick release race one hoping it was just the originals breather hole blocked. When I started the bike and let it get up to temp before turning off and taking cap off there is still the whoosh of air going inside.
There is no external vent tube to check etc so I'm guessing I need to get the fuel pump out... anyone know of anything I may have missed? Cheers
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07 Dt125r, sv650s k8, zx6rr 04

monkeybiker · World Chat Champion Joined: 23 Sep 2014 Karma :

Does it use the overflow pipe as the breather? My bike is designed like that. Check the tube is not blocked or kinked.

robertw95 · Trackday Trickster Joined: 22 Nov 2014 Karma :

I can blow through breather pipe fine no kinks, I had pump off to check for blockages before putting it back on, there is what looks like a pipe inside but wasn't connected to pump ... at a loss here definitely still a vacuum being formed inside tank but the cap I fitted has a small hole I assume is the breather
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07 Dt125r, sv650s k8, zx6rr 04

chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

Put the old cap back on sounds like a crap cap.
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robertw95 · Trackday Trickster Joined: 22 Nov 2014 Karma :

It was happening with standard which is why I changed, its a track bike and this cap was recommended by a friend
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07 Dt125r, sv650s k8, zx6rr 04

chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

robertw95 · Trackday Trickster Joined: 22 Nov 2014 Karma :

Problem is the only tube coming from the tank is an overflow which is clear, From what I could see when I had the pump out there is a pipe inside the tank which I believe is the vent that is blocked, just no idea where it goes to or if its connected to pump etc
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07 Dt125r, sv650s k8, zx6rr 04

robertw95 · Trackday Trickster Joined: 22 Nov 2014 Karma :

Removed one of the seals from cap that appeared to cover breather hole, no more rushing of air Laughing

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07 Dt125r, sv650s k8, zx6rr 04