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Gas coming out of tank vent tube

Old 07-18-2018, 10:06 AM
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Gas coming out of tank vent tube

Hi All, the bike is new to me and I want to make sure this is normal, and/or if there is anything I can do about it. This has happened twice now, where I fill up the tank and park it shortly after. After sitting in the sun for as little as half an hour fuel starts coming out of the tank vent tube (the little line that comes off the bottom rear of the tank). The first time, I think I overfilled the tank, and went over the little bar in the filler hole. The second time, I made sure to be maybe a 1/4" below the bar.

To fix the issue, I have stood the bike up and opened the gas cap to let out the excess pressure, and most recently, parked it away from the other cars at my work and left the cap popped open. I would have though the factory gas cap has a vent in it, but in taking it apart, it looks like it does not. Is my only option to just fill up way less? or do I have an issue with my vent system? is there supposed to be a check valve in the line or something?

Thanks for the help!
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Old 07-23-2018, 06:18 PM
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My bike does this too. Sometimes I try to prevent this by filling up well before my ride or commute is over. Doesn't always work. Would be nice to know if anybody has figured something out.
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Old 07-23-2018, 07:03 PM
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Your tank vent (breather in pic) more than likely need cleared. No way should it build pressure.
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Old 07-23-2018, 09:18 PM
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The only way for air to get or out of the tank is through the breather pipe. There is definitely no vent in the tank cap, you can flip the tank on its back and it won't leak. If the tank breather pipe in the tank has been bent downwards (or has a hole in it) it is possible for the intake to be sitting in the fuel, then any headspace expansion (heat soak from motor or sun on tank) would increase the tank pressure and push liquid fuel out. Maybe get a dentist mirror and see where the end of the pipe terminates.
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Old 07-24-2018, 06:11 AM
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Originally Posted by Wolverine View Post
Your tank vent (breather in pic) more than likely need cleared. No way should it build pressure.
That is the hose that the fuel is coming out of, so it is definitely not blocked. I even blew some air up the hose and heard air coming out of the tank when the cap was open.

Originally Posted by Cadbury64 View Post
The only way for air to get or out of the tank is through the breather pipe. There is definitely no vent in the tank cap, you can flip the tank on its back and it won't leak. If the tank breather pipe in the tank has been bent downwards (or has a hole in it) it is possible for the intake to be sitting in the fuel, then any headspace expansion (heat soak from motor or sun on tank) would increase the tank pressure and push liquid fuel out. Maybe get a dentist mirror and see where the end of the pipe terminates.
Excellent idea! Next time I get the tank close to empty I will definitely try that. Thanks!
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Old 07-24-2018, 10:23 AM
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The tank overflow hose ultimately leads out towards the front of the bike exiting by the lower belly pan nr the starter motor on the left as stting on the bike.

If fuel is coming out from the fuel tap then it could be the diagram has split and it will run out on the black rubber cover under the tank that protects fuel from dripping dirrectly onto the rear cam cover.
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