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Thread: How do I completely drain F700GS fuel tank?

  1. #1
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    How do I completely drain F700GS fuel tank?

    Alright all you F bike experts;

    How do I completely drain the old gas out of my wifes F700GS without riding it? (long uninteresting story)

    Looking for someone who knows.

    Thanks.



    Might be a good thing to have in the Tech Library.




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  2. #2
    I am not sure about completely but I would start by disconnecting the fuel line and using the fuel pump to pump it out.
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    Paul,

    Is there a simple way to run the pump (does the pump run with just key on?) or do you think I should disconnect the wires from the harness and just jump the pump? I don’t want to risk messing with the Canbus or screwing up any electronics.


    Thanks




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    Lee Fulton Forum Moderator
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  4. #4
    Back in the saddle again mikegalbicka's Avatar
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    The complex shape of the underseat tank and the delicate float mechanism make trying to get a siphon or pump hose in there highly inadvisable. Power can be applied to power the pump. There is a lot of info on this - just Google fuel pump controller bypass.

    Sent from my SM-T813 using Tapatalk

  6. #6
    Registered User drneo66's Avatar
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    Quote Originally Posted by 98lee View Post
    Alright all you F bike experts;

    How do I completely drain the old gas out of my wifes F700GS without riding it? (long uninteresting story)

    So you filled it with diesel, eh?
    Current: 2007 BMW R1200RT, 2013 F800GS
    Former: 1995 BMW K75S, 2009 BMW G650GS
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  7. #7
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    Quote Originally Posted by drneo66 View Post
    So you filled it with diesel, eh?

    Well, there was no line at the diesel pump...


    Nope, it's just been sitting way too long and it's going to sit for quite a bit longer after I get my knee replaced.




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  8. #8
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Quote Originally Posted by 98lee View Post
    Well, there was no line at the diesel pump...


    Nope, it's just been sitting way too long and it's going to sit for quite a bit longer after I get my knee replaced.




    Just run it down around halfway and treat with Sta-Bil and Techron, run it in and stop worrying. In snow areas, like mine, bikes sit for months and with a little treatment, resume running fine. Even better if you can use/find non ethanol out there in Kaliphornia.
    Good luck with the knee…..it’s almost day surgery nowadays.
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    A cutaway of the tank illustrating my earlier post.

    Tank cutaway.jpg

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    RadioFlyer,

    Thanks, very helpful!

    To me, it looks like the best thing would be to pull the fuel pump. Then I would have good access to drain and clean the inside.

    I assume that the area below the pump is the lowest part of the tank and there are no baffles that would prevent any of the fuel from going to that point.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
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  11. #11
    Back in the saddle again mikegalbicka's Avatar
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    Quote Originally Posted by RadioFlyer View Post
    A cutaway of the tank illustrating my earlier post.
    It is certainly more complex than my RT tank with the proebeemer.nl float conversion for sure. A trick I used was to take a piece of stiff wire that would hold its shape about half the inner diameter of the siphon pump tube and bend it to easily go where it needs to in the bottom of the tank being careful not to catch on the float itself. Then insert this wire in the siphon pump tube and snake it back in place. I could see through the filler hole with a flashlight because I had removed the fuel cap and filler neck previously. Might not be doable on this model but worked great on my RT.

    Pulling the pump is not too hard either on this RT.

  12. #12
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    Quote Originally Posted by mikegalbicka View Post
    It is certainly more complex than my RT tank
    The F700/800 tanks are more complex than any tank I know of. You can not see or touch any of the inside of the tank through the filler. There is virtually no information on draining these tanks on the internet. But there is info on replacing the pump. That combined with the cutaway that RadioFlyer posted should get me to where I want to go.



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    Lee Fulton Forum Moderator
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  13. #13
    Back in the saddle again mikegalbicka's Avatar
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    Quote Originally Posted by 98lee View Post
    The F700/800 tanks are more complex than any tank I know of. You can not see or touch any of the inside of the tank through the filler. There is virtually no information on draining these tanks on the internet. But there is info on replacing the pump. That combined with the cutaway that RadioFlyer posted should get me to where I want to go.



    I have detail on removing my pump here. Not sure how much is the same for your model but some of it might be helpful. Steps 10 and 17 for fuel pump.

    https://forums.bmwmoa.org/showthread...uel-Strip-2007

  14. #14
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    The tank has to be less than half full before you can open the fuel pump lid. Otherwise fuel will gush out big time.

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    With RadioFlyer’s info and a GREAT video by Best Rest Products, I got it completed this afternoon. Thanks for all the input guys!

    Gary, you need to put this video in the Tech Library: https://www.youtube.com/watch?v=D4k7XOOV1uE

    I have a new found respect for the designer of the F700/800 fuel tank! The tank is not just under the seat. The tank goes from the center of the engine to the taillight. It is over 40” long! It goes under and over and through all the mechanicals of the bike and never gets higher than the bottom of a standard style tank. It all pools right below the fuel pump access hole, so it is easy to drain. Most crud should settle there and is easily wiped out. But getting your hand to the far reaches of the tank is not possible because of all the bends. But I didn’t need to.





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    Lee Fulton Forum Moderator
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