BMW F650GS 2008 Twin fuel tank vent issue

Hi all i am new to the forum. I recently purchased a 2008 F650GS twin iceberg blue for my wife. Yesterday i got a call from her to say she was stuck at the side of the road after engine had cutout just after leaving a roundabout. She stayed calm clutched and parked safely on the hard shoulder, so all good, thank goodness. The fuel gauge was showing about 3/4 full. Engine would turn over but not fire up. On opening the fuel tank cap there was a loud hiss as air was sucked in so we believe a venting issue is the root cause.. Tank quantity now fell. Still would not start so it was also empty. We had brought fuel just in case and it fired up instantly when topped up.
She had been driving the bike in our wonderful Summer of rain over the last number of days. Is there a known problem with the venting system, and any warranty or other sugested fix for this issue. Any assistance much appreciated.
Im planning to get a bike myself and am embarking on the biker beginners course.
Best regards PJ

Have a look on the F800 specific forum and you should find a recent post about this very problem.
As I understand it, it is to do with the "fuel cut-off" device blocking the vent hole up.

Just had another look on the F800 Riders forum.
The post in question is in the F800R section and titled " Your F800R is going to stall".
Worth a read.
ATB.

Hi wust588
Thanks very much for the reply, not sure if this is exactly the same thing. I found the problem tonight, it was the fuel tank vent system check valve. The valve is made from aluminium and had corroded. I removed it found the check valve ball was stuck not allowing any vent air into the tank. Cleaned up the valve P/N 16 11 7 721 943 VENTILATION VALVE and used penetrating oil and an air blower to get it functioning again. To access this check valve you remove the seat and the R/H rear panel (You may have to remove top luggage rack if fitted). Follow the vent hose and the check valve is located under a piece of foam on the pipe just a few inches from the tank vent fitting. The hose continues and exits down around the side stand. It picks up lots of moisture down this low so i think i will shorten it and tye wrap it where it wont be as prone to sucking up moisture. I am going to replace the check valve to prevent the possibility of a reoccurrence in a few months. The fuel pump must have been working hard to work against all the vacum pressure being built up and still amnage to supply fuel until the tank was empty.. I would advise any F650GS owner to replace the valve if they hear any sucking sound when opening the tank cap. I would also replace every 3 years or so to prevent the issue. It is not an expensive part. I will try posting some pictures if anyone is interested. I will run the tank dry again to see if we still have a fuel quantity indication issue.

Best regards PJ

volcane said:

Hi wust588
Thanks very much for the reply, not sure if this is exactly the same thing. I found the problem tonight, it was the fuel tank vent system check valve. The valve is made from aluminium and had corroded. I removed it found the check valve ball was stuck not allowing any vent air into the tank. Cleaned up the valve P/N 16 11 7 721 943 VENTILATION VALVE and used penetrating oil and an air blower to get it functioning again. To access this check valve you remove the seat and the R/H rear panel (You may have to remove top luggage rack if fitted). Follow the vent hose and the check valve is located under a piece of foam on the pipe just a few inches from the tank vent fitting. The hose continues and exits down around the side stand. It picks up lots of moisture down this low so i think i will shorten it and tye wrap it where it wont be as prone to sucking up moisture. I am going to replace the check valve to prevent the possibility of a reoccurrence in a few months. The fuel pump must have been working hard to work against all the vacum pressure being built up and still amnage to supply fuel until the tank was empty.. I would advise any F650GS owner to replace the valve if they hear any sucking sound when opening the tank cap. I would also replace every 3 years or so to prevent the issue. It is not an expensive part. I will try posting some pictures if anyone is interested. I will run the tank dry again to see if we still have a fuel quantity indication issue.

Best regards PJ

Click to expand...

Very interesting

Would it be possible to trickle a drop of oil/wd40 down the pipe from the fuel filler now and then to prevent seizure?

volcane said:

I will try posting some pictures if anyone is interested. Best regards PJ

Click to expand...

That would be helpful. Cheers

F650GS fuel tank not venting

I recently had this issue. It is a couple years after the original post, but I thought I would add what I found in hopes it might help someone else. Had the gush of air entering the tank when opening the cap. Bike would stall at light from time to time. It was not until I rode a friends F650GS (Same year 2010) that I really knew there was a problem. My friends bike had MUCH more power!
So I searched the net and found the above mentioned check valve issue. For your information, and to aid in finding information and a replacement if needed, this is called the "Roll-Over Valve". I found that my ROV was ok, but I did find my problem elsewhere (at a tubing "Y" connector). And my issues was as a result of a clog in that connector. Below I have covered my entire experience; checking roll-over valve as we'll as finding my true problem. I don't think all countries use the charcoal canister' so of course if yours doesn't then that part won't apply to you.

Location of roll-over valve (2010 F650GS):
On the same side as the gas filler cap. You will need to remove the seat, grab bars/rack if equipped. Then remove the long side panel that is to the outside of the fuel cap (two small torx screws), you will see the venting intake nipple under this. Next, remove the small panel that would meet with the back of the seat. Now you can access the roll-over check valve. Follow the tube that comes off of the tanks vent nipple. About 3 inch back you will see a tie wrap holding the tube to the frame of the bike. THAT's The valve that the tie wrap is wrapped around. It is a small aluminum inline valve that is the same diameter as the tubing it is connected to. There is an arrow on the valve that points to the gas tank when you put this back together. Cut the tie wrap and remove the 3 inch section of tubing from the tank vent nipple and remove the tube from the far end of the valve. Now that you have the small section of tubing and check valve removed, check its function by blowing in and sucking on it. If the valve is working you will only be able to blow or suck in one direction. Replace or clean as needed so this valve only allows flow in the direction of the arrow. If you have no flow in the direction of the arrow then the valve is stuck. By the way, my valve was fine. I put a couple drops of oil in it and blew it out with air just for maintainable.

So, I was a bit disappointed that I found a good valve because now I still had a problem. I put my mighty vac on the side of the tube the was going towards the engine and found I could get no air flow. I followed the tube and it connects to the top of the charcoal canister (some counties don't have this, the USA does) if you do have this, it is located on the same side of the bike as the fuel cap, just forward of the rear shock (it's black plastic and a bit bigger than a soda/pop can. I disconnected the tube at the bottom of the canister and BANG! My mighty vac pressure dropped to zero. I found the obstruction to be in the Y connector that is on the tube that connects to the bottom of the charcoal can. If the Y connector is your problem it is very easy to get to and fix without needing to disassemble anything but tube connections. Blew the Y connector out with compressed air, put everything back together and WOW!!! She has been brought back from the dead. This back vacuum in the fuel tank must have been beating my fuel pump up.....

Hope this helps