Author Topic: Need help with fuel leak from overflow vent.  (Read 178 times)

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Offline Dave

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Need help with fuel leak from overflow vent.
« on: October 16, 2018, 07:17:08 pm »
I have a fuel drip from the tank overflow vent tube.
This is what I have done so far to identify the cause.
Since there are two vent tubes, I first of all had to identify which one was leaking. It is the tube that vents overflow from the filler cap area. I plugged the tube. Drip stopped. Unplugged the tub; drip returned. So source of drip confirmed. It is my understanding that this tube is routed internally (inside the tank). Since there is no fuel in the shoulder rim around the cap opening, and the drip persists, it seems reasonable to assume that the tube is compromised somewhere inside the tank allowing gas to leak - probably a tiny pin hole based on the amount of the leak. I also removed the filler cap, plugged the top vent hole with my finger and pressurized the drain hose from the bottom. I was looking for either tell tale bubbles in the tank (it was topped right up) then listening for any sound from a leak. No bubbles but when I put my ear against the tank, I think I could hear a faint bubbling noise (not 100% sure).
So ........ my question is "is this vent hose replaceable?" If not, do I need to replace the whole tank?.
I can't think of anything else to do to diagnose the problem but would appreciate any feedback from anybody who has encountered this situation or might have some thoughts on a solution short of tank replacement. TIA   

Offline gpd323

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Re: Need help with fuel leak from overflow vent.
« Reply #1 on: October 16, 2018, 07:54:07 pm »
I cannot answer all your Q's, but if I fill the tank up over the neck hole and then let it sit on the side stand it will drip gas out the vent hoses. Especially when the engine is hot and heating up the fuel tank as it sits.
Greg Downing
Beautiful Downtown Spanaway
Washington State

Ride while you can.

Offline MAN OF BLUES

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Re: Need help with fuel leak from overflow vent.
« Reply #2 on: October 16, 2018, 09:02:13 pm »
what year is this bike?
Has it sat outside in the weather for extended periods of time?

the vent line you are noting is actually a metal tube, that is welded in place on both ends, inside the tank.... it is not replaceable, in any notable way, as there is no access to it.
Some people have reported that when the bike was stored for extended periods, with a low fuel level, rust was evident on the upper inner surfaces of the tank, and those lines, and i vaguely remember one person did have a pinhole leaker in a tube.

I'd suggest as a possible remedie, removing the tank, pouring out the fuel, invert it and pour the remaining fuel out, and pull the fuel pump off... maybe you can inspect it from that hole..
but repairing it is another story.
If it is indeed a pinhole in that tube, blocking the top hole will do no good, as it above the point where the fuel is entering the pin hole... a real dilemma.

bummer, best of luck on finding a solution, I think a new tank may be needed... but, if you pull the pump, and can see the leak, you may have success using a product like POR-15 to seal the pinhole, using a couple coats. It's a fuel tank sealer, Impervious to fuel, and works great, just have to clean and apply it in layers to the effected area.

30 YEARS OF KAW.....Rich R. (the other one..)  COG 5977  JUSTAMEMBAHNOW
and if you are gonna call me names... it's MR. Analdweeb if you please...

Offline Dave

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Re: Need help with fuel leak from overflow vent.
« Reply #3 on: October 16, 2018, 09:51:03 pm »
Thanks Richard. Your assessment seems to pretty much align with what I have been able to figure out. Not what I wanted to hear but an inconvenient truth is way more useful than a warm fuzzy fib.  LOL.  I will research the repair that you suggested and hope it's not beyond my limited expertise.

Offline MAN OF BLUES

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Re: Need help with fuel leak from overflow vent.
« Reply #4 on: October 16, 2018, 10:45:15 pm »
Thanks Richard. Your assessment seems to pretty much align with what I have been able to figure out. Not what I wanted to hear but an inconvenient truth is way more useful than a warm fuzzy fib.  LOL.  I will research the repair that you suggested and hope it's not beyond my limited expertise.

your welcome,
if you are handy, and inventive/creative, I would think you may be able to fix it... I'm pretty inventive, and would try it myself.
Both those steel tubes come together just rear of the filler neck, and are tack welded together in a couple places along the path, they are also tack welded to a bracket that holds them off the inner surface of the tank, and prevents them from vibrating/flexing.
I would think that any pinhole would be found at one of the points where welding occurred, it's logical, as that would rust first.

if when you pull the pump, and examine the path, and see what I'm talking about, think about this;
If you create a "well" or "containment wall" using modeling clay, that is stuck to the tank wall, and encompasses, and sits higher than the tubes, it can be used as a "mold cavity" that can be filled with the POR-15 product, encapsulating the leaking spot completly... and then peel away the clay "dike" after it's cured, leaving an encapsulated leak repair.
POR-15 pretty much sets up 'firm' overnight, and cures completely within a few days ( when used as a 'coating, pretty much 48 hours, but a 'pool' of it like this may take a couple more days, just to insure it's completely setup.
I know the leftover mixture I had in the can set up solid in a week, and was entirely reliable.. I poured fuel in the can, and let it set after that for almost a month, topping it up occasionally, and it remained unscathed from any effects.

get the smallest can, it's just a cup or so in size..  and mess around with it.

Just don't get any on the paint... it is impossible to remove..
Also be cautious about the fuel level sending unit/float assembly in there...

$15, and maybe you will have a good success...
https://www.por15.com/POR-15-Fuel-Tank-Sealer
« Last Edit: October 16, 2018, 10:53:36 pm by MAN OF BLUES »

30 YEARS OF KAW.....Rich R. (the other one..)  COG 5977  JUSTAMEMBAHNOW
and if you are gonna call me names... it's MR. Analdweeb if you please...

Offline Dave

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Re: Need help with fuel leak from overflow vent.
« Reply #5 on: October 17, 2018, 12:39:21 am »
Thanks again. Whether I decide to do it myself or contract it out, All knowledge is good. I've already spoken to a local rad shop who can handle it if I decide to go that way.