fuel tank "under pressure"

I didn't notice on mine when I filled up a couple of times over the weekend.

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?

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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.

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.

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.

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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.

Derek said:

Like this -

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

ok, where the breather is?

Hedonism said:

ok, where the breather is?

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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 ?

The Scrambler has a different design of cap and may be different but in the case of the SS above and most Ducatis with the same cap the vent is through the gas cap to the rear where it seals over a rubber grommet. Below the grommet is a tube which exits at the bottom of the tank where a rubber hose takes it down below the engine. On most models the fuel filler drain and the vent use the same hose, usually joined with a Y connector below the tank.
Now the Scrambler may use a completely different set up but the odds are it's through the filler one way or the other. If there are any hoses it's worth checking that they are clear and not kinked. I wouldn't attempt to take the cap apart as , like Hui says, there will be a tiny spring and ball bearing in there which will probably fly off into oblivion when you try to dismantle it. Since the bike is under warranty you'd be better to get the dealer to sort it out.

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

Hedonism said:

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

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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.

nope, issue happened before mud session

Hedonism said:

nope, issue happened before mud session

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Forgiven

Hedonism said:

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The breather looks clear to me.

Mine seems ok, will be interesting to hear about the fix just in case

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.

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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.

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