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docc

Fuel tank mystery

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Some of you recall me chasing a funky spooge drip/puddle that I thought was the Crankcase Vent Return Line.

This really did turn out to be something new happening to my tank vent /overflow lines (mine are combined).

IMG_8069.jpg

Seems to be getting worse. It's like my tank is leaking, internally, into these lines. Inspecting inside the tank, it appears the (right side) vent line and the overflow (left side) internal tank lines are coated (with ?) even over wire hose clamps. There are bulges in the vent line (seen upper in this image).

Does everyone's look like this?

IMG_9504.jpg

 

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Internal tank shot of the lines looks fairly normal to me docc. All of my new tanks look like this although the newer internal pump ones look like they might use a different retaining clip. The tanks are made by the rolling mould method(like an ester egg) so everything internally gets coated with tank material.

Maybe its ethanol related? seepage into the lines through the tank material overlaying the vent and overflow lines and through the rubber hoses. Or maybe the cap venting is stuck fully open and venting all the time and the spooge is what remains of the vented fuel after the volatile components have evaporated off. Try having the cap cracked open when the bike is parked with some absorbent paper or something over the inlets to the vent and overflow lines aand see if it still produces the spooge. If it doesnt then the source is via the cap and if it still does its probably via the lines internally.     

Ciao

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Thanks. Yeah, I thought that all looked like Nylon from the roto-mold. Interesting they molded in those internal lines and wire clamps!

Trying to find, and stop, the fuel siphoning. I've defeated my tank vent by pulling out the cap seal to the vent. I've considered replacing the cap. It no longer sits flush (but looks to still seal) and shows some cracking around the latch.

IMG_9503.jpg

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I've also thought how much my (old, tired) tank might be expanding and contracting with temperature change: 95ºF ambient/ fill up with fuel from a 60ºF ground tank/ heat it back up riding then park in 70ºF shop space: tank contracts and spews?

I mean, that sounds rational, but it has never done this before I dried the tank ot during the clutch service two years ago. So, this is "relatively" new behavior.

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I'm running a screw on race style cap to suit an Aprilia. Fitted it about 5 years ago

Ciao 

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47 minutes ago, Lucky Phil said:

I'm running a screw on race style cap to suit an Aprilia. Fitted it about 5 years ago

Ciao 

Does that defeat the vent and the overflow?

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3 minutes ago, docc said:

Does that defeat the vent and the overflow?

No works with the std system.

Ciao 

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What has gone wrong with my vent that it is siphoning off fuel?

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6 hours ago, docc said:

What has gone wrong with my vent that it is siphoning off fuel?

Docc I suspect your cap seal is leaking (it looks a bit ropey near the hinge) and allowing some fuel seepage down the overflow line and into your catch bottle. Try some fuel proof non hardening sealant like Hylomar around the seal with a full tank to see if you still get the spooge(for proof of theory) or better still fit a new cap as it appears from your comments it needs one anyway. 

Ciao 

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