fuel tank "under pressure"

16695 Views 51 Replies 17 Participants Last post by OscarWilde, 8 mo ago

Hedonism

Discussion Starter · Apr 21, 2015

the fuel tank lid is difficult to open..... the inner pressure seals it to the tank and I have to strongly pull out using the lock's cover till air comes in (pppssssssss)

someone else has same issue?

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Hui

· #3 · Apr 21, 2015

Hedonism said:
the fuel tank lid is difficult to open..... the inner pressure seals it to the tank and I have to strongly pull out using the lock's cover till air comes in (pppssssssss)

someone else has same issue?

Sounds like the breather in the cap is blocked and not letting it equalise. As fuel is depleted it creates a vacuum in the tank which can lead to the engine starving of fuel.

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Hui

· #5 · Apr 21, 2015

Derek said:
There were also stories of the tanks caving in on some of the early SSie models. It seems there was a vacuum created in the tank due a blocked breather. When the bike was garaged overnight the air in the tank cooled down increasing the vacuum such that the tank imploded Not a nice sight to open the garage to in the morning. You should definitely get that breather checked.

Yep, I've not seen it personally on a bike but you'r right, I have seen it on a Peugeot with a plastic fuel tank and a Scania truck with aluminium. You would hardly believe the fuel pump would have the power to do it but it can.

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Hui

· #7 · Apr 21, 2015

Derek said:
Like this -

All for the sake of 1mm hole. Looks like the standard cap too.

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Hui

· #9 · Apr 21, 2015

Hedonism said:
ok, where the breather is?

The breather path is integrated into the cap and will consist of one way valve usually with a ball bearing and spring in-case of going up-side down shutting off the flow.
Be careful if taking it apart and take note of how it goes. Maybe the seal is covering the hole ?

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Hui

· #12 · Apr 21, 2015

Hedonism said:
ok.... will tell them on first service I'm going to do soon

Just a thought, after your dirty weekend it could be the breather exit tube below is choked with mud ?
This is what you get for enjoying yourself and taking the piss out of us with your great photos. I don't have much sympathy really.

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Hui

· #14 · Apr 21, 2015

Hedonism said:
nope, issue happened before mud session

Forgiven

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Hui

· #16 · Apr 21, 2015

Hedonism said:

The breather looks clear to me.

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Hui

· #19 · Apr 24, 2015 (Edited)

Hedonism said:
today at 1st service, they blown compressed air into the small hole in the middle of the two nuts on the left. here is picture, you can see it on left (gold spot)

this is the tank breather.

Did it work ?. The reason I ask is because it lets air into the tank as the fuel level drops. The air needs to blow from the outside inward as there is a one way valve in the line. It could actually make it 'worser' by jamming the valve the wrong way.

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Hui

· #21 · Apr 24, 2015

Hedonism said:
He said air was exting from external pipe.... May be it ventilates vapour outside as well. Will revert next refill

You can get valves 'pvv' pressure vacuum vent that vent vapour both ways but not so much on modern vehicles as they need to vent through charcoal filter or re-burn and not to atmosphere. Anyway, I'm sure they've got it sussed out. I hope.

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Hui

· #27 · May 11, 2015

silverluxe said:
You say they blew through the hole with an air compressor.. but isn't the hole supposed to pass air the other way (suction?) Have you tried to trace the mechanical valves in the circuit yourself? I'm curious if someone simply installed a one-way valve in the wrong direction or something..

That's what I said a while back, blowing air the wrong way could actually make it worse if it's the valve ball that's stuck. Or, like you say, it could be the valve in the wrong way round which takes a bit of care when investigating due to springs and wee balls flying out.

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