Aux tank on F800GS

Discussion in 'Parallel Universe' started by Shawnee Bill, Aug 26, 2010.

  1. Shawnee Bill

    Shawnee Bill Long timer

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    I’ve been looking, waiting for someone to post about this, but no one will so here it is.
    My F800GS now has an extra 4 gallons of fuel on board, relatively low cost installation.
    Tour tank onboard.

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    First step was to aim a drill at my $900 tank and maybe ruin it, I really wanted to do this with my eyes closed but I just bit my cheek and drilled. This will be the entry point to refill the main tank on the fly.

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    If you look closely at that second picture you can see the tank is double walled, I was a bit worried about sealing the bulkhead fitting because of that but so far, so good.
    Why there? Well, it seemed to be an easy place to get to without dismantling the bike, but mainly I needed to be able to reach the inside nut on the bulkhead fitting with a wrench.
    Before I drilled I stuffed a towel into the tank to catch any drill shaving that fell inside the tank, worked, they were all right there and easy to clean out.

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    Next I had to be able to start the interior washer and nut with out dropping them into the tank, so I threaded a zip tie through the bulkhead fitting and slid the washer and nut down the tie, no way they could miss their target, then it was easy to reach in and get the nut started. I coated the Teflon washer with gas proof thread dope before putting it in. I was worried about a leak there and it is holding well so far.

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    Bulkhead fitting installed, it looks somewhat exposed here but is protected by the luggage rack and cases when finished.

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    Gas line and luggage rack installed. You can see how I mounted the tank here. I found a sheet o f aluminum, bolted the tank to it. The plate is secured in the back by the two rear bolts that hold the grab rail on, the front I bolted a 1/8" x3/4" steel bar to the plate, bent loops to wrap it around the grab rail and clamped it in place. It is real solid.

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    Left side view. Valve is on this side, where it is located is easy to reach while riding. When the distance to empty gets below about 40 miles I open this valve and watch the DTE mile increase.

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    #1
  2. digdesign

    digdesign Hack

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    Awesome!
    How are you managing the venting? I see you have a hose. Is it valved?
    #2
  3. reinerka

    reinerka Been here awhile

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    Nice job. 4gal should be another 200 miles - something the F800GS really needs to be able doing in order to earn the adventure title.

    Only major problem with those fuell cells that I have is that they take luggage room on the back (and removing the ability to carry a passenger). The other is that you still have to open/close petcocks to drain from the aux to the main.

    Reiner
    #3
  4. AlanI

    AlanI Adventurer

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    I take it that this sort of thing is legal in Oklahoma then? For a minute I thought that I was looking at a bike located somewhere in the far reaches of India LOL. :D
    #4
  5. Shawnee Bill

    Shawnee Bill Long timer

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    That hose you see is merely the vent from the aux tank. Tour tank comes with an open vent tube off the filler neck, I will route that into a catch bottle soon. Also I will leave some air space in the tour tank when I gas up.

    The venting that worried me was the main tank, it has a check valve on it's vent so that it will pressure up but lets in air as the fuel level goes down. Because of that if you open the valve with a full main tank to let fuel from the aux to main it can not push gas out the vent but will pressure up the main tank. The computer doesn't seem to like that very much and will not run below about 2000 RPM, it just dies when you back off the throttle. Not good.
    However, if I wait until the main tank is fairly low, below a gallon, then open the valve from the aux tank it will slowly drain into the main tank. Best to do that in stages, drain a coupe of gallons into the main, close the valve and burn that down and then open the valve and let it all run down. Works.

    I wonder if I should put a check valve in that vent line as the main tank vent has?
    #5
  6. Shawnee Bill

    Shawnee Bill Long timer

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    I agree with what you say are problems, but blame that on BMW, they should sell this bike with at least a 6 gallon tank.
    Since they left it to us to deal with this is what I did. The other option is the Touratech tank but that costs about 10 times what I spent, and it's a LOT more work. And you have to take the bike half apart.

    I can pack all my luggage, including camping gear in my Pelican bags, top case and larger tank bag. I don't tie on anything any more.
    As for a passenger, I don't often carry one and for sure not on longer rides, but if need be I can remove the aux tank in about 10 minutes. Not ideal I admit, however I am no longer constrained by gas station locations. An extra 4 gallons doesn't prevent you from running out of gas, it just delays it a while. DAHIKT :lol3 :huh
    #6
  7. Shawnee Bill

    Shawnee Bill Long timer

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    Several years ago Oklahoma threw out vehicle inspections so anything is legal, or at least you can get away with almost anything :evil

    Not only that I am pretty sure this will pass IBR and Team Strange specs when I get a catch bottle attached. :clap That's actually more important to me than some government rules. :eek1
    #7
  8. digdesign

    digdesign Hack

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    I guess you could open the filler cap on the main tank to relieve the pressure. But im sure you already thougt of that. Would be nice to have a solution where you dont even have to stop.
    #8
  9. TireIron

    TireIron n00b

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    Lot braver then I would be doing a project like this drilling hole into $900 gas tank. Why not create a mount for several rotopak gas tanks instead of aux tank?

    -TI
    #9
  10. Shawnee Bill

    Shawnee Bill Long timer

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    I drilled a couple of practice holes in an old gas can before I touched the bike's tank. It's a similar consistency plastic. I even tested the bulkhead fitting on the old gas can.

    I thought about rotopak, but that is not allowed under most endurance rally rules, also it's much more convenient to just reach back and turn the valve, no stopping and fooling with gas cans. Then have to fool with filling them back up.
    I've carried spare gas in cans up and down the Dempster and all the way back to Oklahoma full of gas, didn't use them because it was easier to just hope I made it to the next gas because I didn't want to stop and fool with a gas can.
    #10
  11. Shawnee Bill

    Shawnee Bill Long timer

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    I don't stop. The valve is easy to reach while riding, just reach back with my left hand and open it. Then watch the gas gauge climb back to full. When the gauge reads full just close the valve, keep riding, repeat as necessary because the gauge reads full with about 1/2 a tank, pretty simple. Stop for things other than gas, don't be constantly monitoring your gas and looking for the next station.
    #11
  12. Shawnee Bill

    Shawnee Bill Long timer

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    Figured out what to do with the vent line. Works great teed into the main tank vent line. Got to be sure to tee in ahead of the check valve in the main tank vent line for it to work. There's a piece of plastic covering this up.
    That black hose going up out of the picture goes to the vent on the aux tank.

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    #12
  13. YamWOW!

    YamWOW! Been here awhile

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    I would rather have beer in it and walk the rest of the way.:D
    #13
  14. oclv454

    oclv454 Been here awhile

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    I was going to ask you why all the drilling and plumbing when you could just fill the factory tank from your auxiliary tank through the normal gas filler. I thought I was hard core, but you have my respect for not wanting to stop for 700 to 800 miles!
    #14
  15. Shawnee Bill

    Shawnee Bill Long timer

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    I have carried spare gas in the past but found I never used it, still made sure I found a station to gas up at. The F800GS will barely make 200 miles before you're walking unless you keep it just over a walking pace. An extra 4 gallons just frees my rides from being controlled by where the next gas station is. I stop just as much as the next guy but where I feel like stopping, not where I have to to gas up.
    Cross country on the superslab I do like to go at least 200 miles between stops though. :wink:
    #15
  16. muskieken

    muskieken Been here awhile

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    that's some great thinking outside the box. looks great to me. it' just needs a paint job.
    like a fosters or heinkin beer keg.
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    or
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    looking for something that matches the orange color, looked
    #16
  17. Dave92029

    Dave92029 Been here awhile

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    I have always tried to keep dirt, etc. out of my gas tanks. When you drilled the gas tank, I assume that you drilled into the tank. Therefore, how did you prevent the contents of the hole from getting into your gas tank? :huh

    I assume that a small shaving could get stuck in your fuel line? :cry

    It's a cleaver, inexpensive solution, but.... :evil

    Ride safe, and have fun! :D
    #17