[silverluxe]

Do the European Scramblers have the Evap canister system like the USA spec ones do?

I have not had this problem yet. I've only run my tank to about -2 gallons of gasoline though, rather than empty, but there is no suction when I open it.

 

[DJKham]

This happens on all my Ducs but the "force" required to open the fuel cap is nowhere near anything you're describing. When opening the fuel cap, it's normal to have negative pressure (vacuum) built up in the tank and to hear a "sucking" noise as air rushes in. If you're having to pull on it with any amount of force, something is wrong. There is a breather hose as others have mentioned so you should check that first to make sure it's not pinched/clogged.

If the negative pressure gets high enough, it can cause stalling problems so I would get it looked at quick.

I did a little searching and there are also threads from other bike forums that document this quite extensively:

Gas tank developing negative pressure - I-BMW.com

Hope that helps.

 

[Hedonism]

I sitll have the issue....

I should go to dealer next week, will try again and in the menatime I'll ask to order a new gas cap, probably the breather is out of order.

p.s. EU bikes do not have canister system

 

[truant]

I sitll have the issue....

I should go to dealer next week, will try again and in the menatime I'll ask to order a new gas cap, probably the breather is out of order.

p.s. EU bikes do not have canister system

Did you get this resolved? I have the same issue, as from Day 1. Due to it being August in Spain it is difficult for me to get the bike to the dealer so I took a look myself, removed the tank cap assembly.

Underneath it are the 2 vents, copper tubes that go through the tank to the underside and onto rubber hoses. I checked these from the top and both are blocked. I dripped some fuel into them and they filled up, not drained away, then I used a bike pump and some plastic tube to check blowing air into them. I could get a very faint release of air at quite high pressure, certainly not free flowing.

I haven't removed the tank yet to investigate further as I'm not sure if I should stop now and leave it to the Dealer to investigate when I can get it to them.

As we both have Urban Enduros fairly early off the production line, in the EU market, I think if you had a manufacturing defect then there is a good chance my tank is in the same batch.

 

[Vincelp]

Underneath it are the 2 vents, copper tubes that go through the tank to the underside and onto rubber hoses. I checked these from the top and both are blocked. I dripped some fuel into them and they filled up, not drained away, then I used a bike pump and some plastic tube to check blowing air into them. I could get a very faint release of air at quite high pressure, certainly not free flowing.

Did you check whether the rubber hoses were not pinched somewhere ?
If you disconnect them from the underside of the tank, do the copper tubes become free or not ?

 

[truant]

Did you check whether the rubber hoses were not pinched somewhere ?
If you disconnect them from the underside of the tank, do the copper tubes become free or not ?

Yes that is the next check, but I am interested to see what the outcome of the OP was on his one.

 

[Hedonism]

last week ends, I did 1100 kkm and several refuelling, abt one each 100 / 150 kms.... every time the tank was under pressure...... will call my dealer

 

[Vincelp]

last week ends, I did 1100 kkm and several refuelling, abt one each 100 / 150 kms.... every time the tank was under pressure...... will call my dealer

Yes, don't go on driving it like that, because you may "crunch" your tank, if the pressure becomes really too low in it.
Your dealer will certainly check first that the tank vaccum are free. It is very easy to pinch one the rubber hoses when mounting a tank.

 

[kjs]

Someone had mentioned somewhere that this can happen if you fill your tank too high...I think the manual states something similar.

It doesn't happen to me often, but when I top it off a little higher than I anticipated I do tend to notice a the vacuum when unlocking the cap.

Edit: The manual doesn't mention anything about a vacuum. It only indicates not to fill the tank above the bottom of the filler rim.

 

[kjs]

To add to my previous post:

The manual doesn't mention anything about a vacuum. It only indicates not to fill the tank above the bottom of the filler rim. There may be cap vents just above the bottom of the filler line, according to the picture. Blocking those with gas would probably cause these symptoms.

 

[Vincelp]

The manual doesn't mention anything about a vacuum. It only indicates not to fill the tank above the bottom of the filler rim. There may be cap vents just above the bottom of the filler line, according to the picture. Blocking those with gas would probably cause these symptoms.

I don't think so. I think that, if you fill the tank too much, you will just loose some gas by the vaccum (when it works properly).
It already happened sometimes on my previous Ducati ST2 : after filling too much the tank, specially by hot weather, I could notice some petrol under the bike, where the vaccum was ending.
If the vaccum system was made in a way that it doesn't work when the tank is too much filled up, it would be a huge mistake !

 

[kjs]

I don't think so. I think that, if you fill the tank too much, you will just loose some gas by the vaccum (when it works properly).
It already happened sometimes on my previous Ducati ST2 : after filling too much the tank, specially by hot weather, I could notice some petrol under the bike, where the vaccum was ending.
If the vaccum system was made in a way that it doesn't work when the tank is too much filled up, it would be a huge mistake !

You mean gas was being pulled through the breather? My olde Honda tends to piss that way too. You're right that probably would happen first.

 

[truant]

Here are some pictures of what I am talking about.

1. The cap assemply removed and I've put some fuel there to see if it will drain, but this shows they are blocked:

2. Here you can see the slot cut in the cap assembly to drain away any spillage while filling or rain while riding:

3. Here is a shot of another slot cut inside the taper that mates to the inner bung. The purpose of this slot is to equalise the tank pressure with ambient, by connecting the inside of the the tank to the outside of the cap assembly, and to the drain tubes.

4. The whole assembly is sealed to the tank recessed surface with a rubber gasket:

5. This looks like some kind of labyrinth vent to allow vapours to equalise without losing fuel. It may have a light spring check valve in it:

6. But none of the above will function properly if the vent tubes are blocked. This is how I tested that with a bike pump:

7. Here is a screenshot taken from the workshop manual showing the 2 copper vent tubes coming out of the bottom of the tank:

I suspect a) these are blocked inside, b) they had some protective dust caps that were not removed prior to fitting the hose to them or c) the hose itself is pinched somewhere. But, it seems strange that both tubes are blocked unless they join together by a hose manifold.

Now it's also clear how water fills the recess, doesn't drain away, and then when the cap is opened, it has no where to go but inside the tank, and is helped in there by the unvented tank "sucking" it in there also.

Unfortunately, I'm working away and just ran out of time to lift the tank properly to take a look this weekend.

 

[Vincelp]

You mean gas was being pulled through the breather? My olde Honda tends to piss that way too. You're right that probably would happen first.

Yes, the breather is for gas and air :
- gas to go out when the tank is too filled or heat tends to produce gas evaporation
- air to come in to replace the gas when it is sent to the motor

 

[truant]

OK, so I had a chance to investigate this further, here are the results:

Essentially, it's a vent hose routing problem. Either the were not routed properly from the factory, or when the dealer fitted my Termi high pipes, they may have removed the tank for access and screwed up the hose routing putting it back on.
1. So with the tank off, you can see the kinked hoses. They have be routed aft of the airbox rubber elbow, when they should be forward.

2. Here they are routed correctly in front of the elbow. The problem is you have to put them on the tank first, and as you put the tank into position, you slide the hose past the elbow. I use a bit of WD40 to help them slide past.

So I removed the tank fully, emptied it out of the old fuel, and put it back per the above. Tested the vent tubes with the cap assembly off and it's fine, put the cap assembly on, refueled it, and spilled some fuel on purpose on the drain/vents, it drains perfectly.

It's just something that will affect anyone who removes and refits the tank as the easiest option is to let the hoses stay routed aft, but then they bend on themselves and block.

By the way, I found the need for a special tool as per this thread to be BS. I followed the workshop manual and pushed the connector in to release the hose fitting, and it came out fine. I made sure the tank was fairly empty first but it seems the fittings seal off when the tank is off anyway.

Here is the photo from the manual:

 

[greer]

Thanks for following up on this; I just got my bike and only filled up one time, but I'm nearly certain I heard a whoosh of air so I've had a twinge of worry in the back of my mind. And very glad to hear you were able to release the QC with no drama, but it makes me wonder if your bike has a new, improved version---seems like it gives everybody else absolute fits. But looking at the manual you'd think it's simple as can be, as you said. Did you go about things in any particular way? Thanks again.


Sarah

 

[greer]

Still thinking about this business with the fuel pump connections, here's something I read about disconnecting fuel pumps in general, this is a copy&paste from a Moto Guzzi discussion:




"There is a secret. I had the same problem with the Triumphs I've owned and my Aprilia.

- Left up the back of the tank and disconnect the electrical line to the fuel pump.
- Stick in the key and run through a start sequence.

You have now relieved the fuel pressure in the line and it will be much easier to remove. Much."




I have no clue and dread the thought, but hoping maybe this will help when the time comes.


Sarah

 

[truant]

Thanks for following up on this; I just got my bike and only filled up one time, but I'm nearly certain I heard a whoosh of air so I've had a twinge of worry in the back of my mind. And very glad to hear you were able to release the QC with no drama, but it makes me wonder if your bike has a new, improved version---seems like it gives everybody else absolute fits. But looking at the manual you'd think it's simple as can be, as you said. Did you go about things in any particular way? Thanks again.


Sarah

Hi Sarah, Mine is a european Urban Enduro, built about March, so one of the early ones I believe. I wouldn't say it was easy to get those fittings to release because when you have to lift the tank and get your hand in there to do it, but I persevered and eventually it worked as described in the manual.

It's well worth taking not of this whole issue because if you lift the tank to do anything, I believe there is a very good chance to route the vent hose wrong and have this issue. If I had some 6mm (1/4") tube on me, I would actually have cut the vent hose below the frame horizontal tubing and then when I need to remove/refit the tank, that is where I would be disconnecting it. It's quite tricky to get the hoses on the tank tubes and route properly.

I reckon many people would have this "problem" and not realise it, or not pay attention, but as mentioned earlier if you get rain, then the Cap cavity fills with water, doesn't drain away, and next time you open the cap the water has nowhere to go but in the tank, and is helped by suction from the unvented tank.

 

[greer]

All noted, now I need to carefully take a peek under the tank. Thank you again for posting up the details.


Sarah

 

[truant]

All noted, now I need to carefully take a peek under the tank. Thank you again for posting up the details.


Sarah

Sarah, if I was you, I would take the cap assembly off (4x 4mm Allen screws) and get some vinyl aquarium tube that fits nicely in those copper tubes and see if you can blow some air through. Like in this pic, only you should be able to blow with air from your mouth no problem. If you have a blockage, then check out the drain hoses routing under the tank.

By the way, I had 3 fills over the weekend and the suction/pressure problem is completely resolved.