high pitch whine/sound coming from fuel tank


I've noticed a very, high pitch whine/sound coming from my fuel tank when I turn the bike off and remove the key.
After I do some riding and get back to my garage & park the bike, I usually go over it.
Make sure nothing in tires and wipe the bike down.
But I have noticed a very high pitch sound from the fuel tank.
WHen I open the gas lid then close it, the sound goes away.
Anyone else experience this and knows why?


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Negative pressure from the fuel tank because it has a vacuum in it. Not sure if there is a fix, but it is a common issue that is pretty normal.


never heard of it on bikes who's tanks are venting properly...check the routing of the vent lines..sometimes they nipped under the tank or nipped as they pass down by the engine/gearbox.
To double check them get a piece of rubber hose a bit broader and push it over the end of the vent and blow into it....it should be really easy to blow since its meant to just be an open hose...any effort means theres a bit of a blockage.

E Zurcher

Hoses are at the right rear of the tank. They route down to the sail fairing underneath. Lift your tank and prop it up and you should be able to get to them. I think there is an air intake in the gas cap. Yours might be plugged because there should not be any vac in the tank at all. There may also be a charcoal cannister purge issue for the vapors going on if your bike is E33 spec.


I'm sure it is from fuel vapors expanding in the tank. They must be pushing out past the fuel cap gasket. Happened quite often on my 08 ZX-18 always on a hot day after a good ride and then shutting the motor down. One day, found a glob of waxy lookin goo on the ground under the drain hoses. Has not hissed since.

My busa fuel tank never hisses and I can tell you the fuel tank overflow is pretty sensitive. It will start to drain at the pump if I fill the tank up into the filler neck. I'd say you have some sort of blockage in a vent tube or an overflow. I don't think this is a serious problem. Just annoying to listen to. I'd still try to fix it.


Thanks fellas.
That was the problem.

In this pic the larger hose was not connected and the smaller one was crimpled/twisted.

Strangly tho, I found another hose that was not connected and tied to the other smaller hose that was crimpled.
After following the hoses, it appears the two that are tied together (but one connected) go down and meet/connect into another larger hose that follows down to the bottom of the bike.
Sort of like a Y
I was gonna go to pep boys and match up some fuel lines and clamps.
In the mean time, I did untwist/uncrimple the one hose and connected the larger hose that was off and the sound is gone.

Here's the pic that was posted in the thread and the other pics are from my bike.

Here's the pic from the thread that you guys posted for me



And here's the pics of my bike
as you can see, I have two lines that are off and one crimpled.
I connected the larger hose and I'm gonna make the one the one that is a Y, make that a straight hose and connect it.
I really dont see the purpose in having a Y hose with only one end connected to the tank.
BUT, it appears thats correct since it's in the above pic


Well after looking at the service manual, it appears that hose (Y) is correct.
So I wont make it into once hose, but make sure it's not twisted or crimpled...
And according to the image below, it was the fuel tank breather hose that was the problem..