1150 GSA pressurised tank

[Robnob]

Rode down to petrol station and back just to fill tank ready for Austria trip. I wanted a full tank so kept rocking the bike on the centre stand each time it was 'full' to overcome the airlock at the top part of the tank, as per usual. I then put the bike straight back in garage which I haven't done before. When I went out there later the garage stank of petrol and it was dripping from the overflow. I opened the petrol cap and a fountain of the stuff shot up under pressure. I cleaned up and left the cap open and when I went back out to check a few hours later the level had dropped to the bottom of the filler neck again. When I've brimmed the tank before I have always carried on the journey and used some of the fuel straight away. I only rode 1 mile back to my garage so what could have pressurised the tank?

The overflow pipe was only dripping slowly and does not drain rain water away from the tank neck either. I have blown up the pipe and all seems clear.

Any ideas on either point gratefully accepted.

 

[MattW]

Rode down to petrol station and back just to fill tank ready for Austria trip. I wanted a full tank so kept rocking the bike on the centre stand each time it was 'full' to overcome the airlock at the top part of the tank, as per usual. I then put the bike straight back in garage which I haven't done before. When I went out there later the garage stank of petrol and it was dripping from the overflow. I opened the petrol cap and a fountain of the stuff shot up under pressure. I cleaned up and left the cap open and when I went back out to check a few hours later the level had dropped to the bottom of the filler neck again. When I've brimmed the tank before I have always carried on the journey and used some of the fuel straight away. I only rode 1 mile back to my garage so what could have pressurised the tank?

The overflow pipe was only dripping slowly and does not drain rain water away from the tank neck either. I have blown up the pipe and all seems clear.

Any ideas on either point gratefully accepted.

The tank breather is actually an internal plastic device (circled in red in the picture below). This thing has a little hole in its top surface and is connected via a hose to the inspection cover on the inside of the right hand tank lobe and from there to the tube which exits next to the right hand footpeg.

If you really try hard to fill the tank (or have done the 'filler neck mod') then you'll actually fill above the level of the internal breather device. This doesn't matter if you immediately ride and use some fuel but as you've found out, if you just park it up, it'll leak and possibly pressurise the tank due to the breather device being covered by fuel.

You should be aware that there are two 'drain hoses' which run through the tank and exit by the footpeg - one is the tank neck water drain, the other is the tank breather as described above. These are independent and not connected in any way (you might also have a battery breather hose as well, making three hoses by the footpeg).

 

[Steptoe]

Have you done the filler mod so you can squeeze in another ltr and a bit ?

If so you never brim it and park up. Brim it and ride.

Even filling a non modded tank to the brim then parking it will cause overflow. The fuel heats up as it circulates through the fuel injection system causing it to expand - hence your leak.

 

[sockpuppet]

Its like a liquid form of boyles law. Its why tankers are designed with proper ullage space in the top of the tank to cope with expanding liquid as it heats up.

Transfering liquid from one larger tank to a smaller tank will almost always result in an increase in temp of the liquid.

 

[Robnob]

Every day's a school day! Thanks all for taking the trouble to educate me. I haven't done the filler mod but I do tend to rock and fill, waiting for the glug from the airlock each time. I've left the filler cap just resting in position for now in case of expansion if the garage gets hot. I won't click it down until I put the tank bag back on and head for Dover at 2am on Saturday

 

[MattW]

Every day's a school day! Thanks all for taking the trouble to educate me. I haven't done the filler mod but I do tend to rock and fill, waiting for the glug from the airlock each time. I've left the filler cap just resting in position for now in case of expansion if the garage gets hot. I won't click it down until I put the tank bag back on and head for Dover at 2am on Saturday

If I completely fill my 1100 I have to park it on the centrestand - the sidestand puts the breather 'underwater' and it drips fuel

 

[Surrey Yeoman]

The overflow pipe was only dripping slowly and does not drain rain water away from the tank neck either. I have blown up the pipe and all seems clear.

I also had a problem with rain water / washing water sitting round the filler hole and even draining into the tank when I opened the lid on my 1150gsa.

Turned out that the metal part of the drain pipe had corroded internally where it's welded to the inside of the filler flange insert. Despite much poking and prodding with various bits of wire I couldn't clear it and had to buy a complete replacement insert.

Might be the cause of your water drain problems?

 

[Robnob]

I also had a problem with rain water / washing water sitting round the filler hole and even draining into the tank when I opened the lid on my 1150gsa.

Turned out that the metal part of the drain pipe had corroded internally where it's welded to the inside of the filler flange insert. Despite much poking and prodding with various bits of wire I couldn't clear it and had to buy a complete replacement insert.

Might be the cause of your water drain problems?

I'll have to investigate further and have a poke around when I come back from hols. I usually end up opening the filler cap carefully after rain / washing and then using tissues to wick up the water but invariably some of it goes in the tank. Not good!

 

[Michael R1150GS Adventure]

Have you done the filler mod so you can squeeze in another ltr and a bit ?

If so you never brim it and park up. Brim it and ride.

Even filling a non modded tank to the brim then parking it will cause overflow. The fuel heats up as it circulates through the fuel injection system causing it to expand - hence your leak.

I did this on a hot ride past Narbonne.
Shat my pants when I parked the bike up after filling it, went into garage shop to buy some water, came out and fuel was dripping out of the pipe... I stupidly opened the filler cap up and POOM! Pressure pressure pressure.

Never did it again.

 

[motobiker]

Why on earth would you need to brim a GS.. any GS for a trip from WORCESTER to the channel beats me completely.

I filled up my tank on its sidestand to the cut-off... and rode to the chunnel from here in Nottingham.. got off the M20 at Ashford Jct 10 and popped to the Tesco which is right nect to the Mway and refilled.. and then didn't need to fill again till Luxembourg. (CHEAP 1.11 euros a litre) Which then got me down to Bad Wildbad in the Black forest.

No need to Brim the tank at any time for me.. and I've just the ordinary 1100 metal tank.

so even less of a problem with your extra 8 litres!!

 

[Steptoe]

Why on earth would you need to brim a GS..

So you can stop when you want to rather than when the bike wants to.

 

[motobiker]

So you can stop when you want to rather than when the bike wants to.

ah.. of course. clever editing mr man. By the time I was at ashford I wanted to stop anyway... that Tesco is everso handy. and just 12 miles from the Chunnel.

If I was on a bimble that might exceed the usual range then I would definitely brim the tank.. I did just that in Slovenia..

But.. I ask you. worcester to the channel? that would mean a refill in france.. or Belgium which is more expensive than here!

still seems a bit off to me..

 

[MattW]

I have some sort of fuel OCD - I start to get twitchy when I get below half way on the gauge (actually about 2/3rds used on my 'not very linear at all' 1100 gauge)

I haven't done the tank neck mod though - mine drips fuel from the breather if I just fill it to the bottom of the tank neck and put it on its sidestand

 

[motobiker]

I have some sort of fuel OCD - I start to get twitchy when I get below half way on the gauge (actually about 2/3rds used on my 'not very linear at all' 1100 gauge)

I haven't done the tank neck mod though - mine drips fuel from the breather if I just fill it to the bottom of the tank neck and put it on its sidestand

I wouldn't do the tank neck mod... I can't remember what exactly it was.. but I do remember it has an unforeseen consequence that isn't a good one.

After my tank swap the float thing is misaligned... and I can't be bothered to fix it. I now fill up when the light is on.. more because it irritates me than anything else. And can usually squeeze 16 litres in.. so yes, quite badly misaligned. On the trip I used the odo.. and filled up around the 180 mile mark.. which left a good 40 miles leeway. (plus if absolutely necessary.. the couple of litres that never gets used in the bottom of the LHS lobe.. of course.)

 

[Firefox]

I've left the filler cap just resting in position for now in case of expansion if the garage gets hot.

Petrol vaporises at normal temp and pressure. It is heavier than air and rolls along ground and into drains and gullies. Leaving the tank open could literally be setting a fuse as the flammable vapor spreads rapidly unless dispersed by wind etc.

And petrol vapor which ignites will usually flash back to the source