Internal Tank Vent Hose Leaks

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motoyoyo
Minimoto racer
 
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Internal Tank Vent Hose Leaks

Postby motoyoyo » Fri Oct 18, 2019 10:46 pm

I searched through the many fuel tank leak posts and have not seen the issue I am having with my 2008 990 SDR. I have had the slow dribble from the external rear vent connector, especially with a full tank. I replaced the rubber gasket that helped, but am having the dribble again, even with the tank lid cracked open to relieve any pressure buildup. Today I removed the fuel lid entirely and used compressed air to blow through the two vent lines to check for blockage. To my surprise, there was air blowing inside the tank from the internal lines connecting the fuel lid to the two external vent fittings. Upon closer inspection, the internal lines are hard and deformed with several spots that are leaking. This is going to be a real pain to fix, if it is even possible. These internal hoses are not on any part diagrams and are likely only replaceable with a whole brand new tank, which I am not going to do. Just wondering if anyone has had to deal with this situation before and may have some possible suggestions. I'll take a closer look inside after I empty some fuel on the next ride.
2008 990 SDR US, Full Titanium Akro, Rottweiler Airbox, SAS Blockoff

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RichUK
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Re: Internal Tank Vent Hose Leaks

Postby RichUK » Sat Oct 19, 2019 6:52 am

I wonder if the higher Ethanol content in your fuel has caused this.

Anyway, sorry but I can think of a way around this other them sealing them up and putting in a different venting system.
Some bikes vent through their fuel caps so maybe there is scope for that.

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motoyoyo
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Re: Internal Tank Vent Hose Leaks

Postby motoyoyo » Sat Oct 19, 2019 7:38 am

RichUK wrote:I wonder if the higher Ethanol content in your fuel has caused this.


Yes, definitely due to ethanol in our fuel. The tank has expanded as well and has to be leveraged in place to get the mounting bolt back in. The internal vent lines seem to be leaking mostly near the top so far. I usually only notice the fuel dribble at the rear external vent fitting with a full tank. I am going to first attempt to seal this fitting and gasket and run the vent line so that it allows any fuel to drain without pooling. Hopefully this will give me some temporary relief so I don't have to park the bike outside the garage due to gas fumes.
2008 990 SDR US, Full Titanium Akro, Rottweiler Airbox, SAS Blockoff

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RichUK
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Re: Internal Tank Vent Hose Leaks

Postby RichUK » Sat Oct 19, 2019 9:47 am

I think all the tanks change shape & expand when removed.
Just yesterday I had to use my largest screwdriver (with tape on the blade) to lever the tank in so it would go past the headset and then again to align the thread for the bolt.

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No. 47
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Re: Internal Tank Vent Hose Leaks

Postby No. 47 » Sat Oct 19, 2019 10:58 am

Not sure which rubber seal you have replaced or why the problem persists with the cap open, but the only solution which worked for me was to dismantle the fuel cap and remove the flat rubber seal within.

This appeared to allow the tank to vent and probably allows fuel to leak out through the cap if tank overfilled or bike on it's side - if so, removing this seal should allow you to leave the internal vent and drain pipes in place without repair, although it may be necessary to seal the drain hole in the fuel tank cap insert.

Also:

viewtopic.php?f=5&t=25127&p=310987&hilit=fuel+cap#p310987
viewtopic.php?f=5&t=19887&p=238643&hilit=fuel+cap#p238643
viewtopic.php?f=5&t=27618&p=334833&hilit=fuel+cap#p334833
'08 ex-Battle race KTM Superduke 990 R No.47
'08 OE KTM Superduke 990 R
'01 Ducati 996S

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05DUKE
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Re: Internal Tank Vent Hose Leaks

Postby 05DUKE » Mon Oct 21, 2019 9:28 am

I had the same issues aligning my tank awhile back, until
I got given some aftermarket tank brackets which changed the
position of the tank just a wee bit, tank now goes on so easy.


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