The superlative siphon sucker reborn.

Discussion in 'GS Boxers' started by Twilight Error, Nov 18, 2012.

  1. Twilight Error

    Twilight Error Going nowhere slowly

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    So there are quite a few of us who own 1100 and 1150 GSs that don't have an ADV tank and its fancy-schmancy crossover line. I happen to be one of them, and after a bit of of digging through the archives for a post that described how to build an internal crossover, I found it here. The picture link, however, is no longer functional.

    So here is my build of this device, with a handful of minor tweaks.

    Parts:
    I bought most of the components from McMaster-Carr. McM-C is an industrial supply house that will sell and ship anything to anyone with a credit card that doesn't bounce. They've got everything from a 2lb bucket of 70% moly paste to telephones. McMaster is the bomb. If you know what you're looking for, chances are its in the catalog.

    Anyhow.

    Tubing:
    PN 5187K75. QTY 5'. Yellow PVC tubing, rated for use with gasoline. It is very flexible and does not hold much of a bend.
    Brass fittings:
    PN 5346K36. QTY 2. You'll actually discard most of this fitting. Cut the threaded portion off first, then remove the swaged collar that remains. This gives you a stub of barbed fitting with just a bit of weight. These keep the tubing in the bottom of the tank.

    PN 91355K49. QTY 1 pkg. Just a 1/2" brass barbed tee. Nothing special, move along. You'll get a package of two.

    PN 7775K64. QTY 1. This check valve has a .3 PSI opening pressure and Flouroelastomer seals - they are immune to immersion in gasoline. It is also capable of being mounted in any orientation.

    .030" Monel lockwire. I used it because I'd salvaged a remnant spool out of a scrap dumpster at work. Any lockwire will do if you don't have easy access to Monel.

    A stub of 1/2" OD fuel hose. If I'd been smart, I'd have also bought PN 546K57. But I wasn't, so I used a stub of fuel hose jammed into the check valve end and pasted in place with JB weld.

    Got your parts? Good. Now, stick a finger down your throat and get to work.

    First, remove the torx screws holding the gas cap in place. If you've got an 1100, remove the allen screws. With the cap off and the filler neck loose, pull the filler neck up and out. The 1150 has a breather valve attached to the neck base with two struts. There are also two hoses attached - one to the plate for the water drain, one to the overflow for the charcoal canister you removed years ago. They can stay attached, there is enough slack they just pull up and out of the way.

    While this dries out, start assembling your siphon:
    Cut the hose into two 24" and one 6" pieces.

    Cut the brass male nipples on the barbed side of the wrench flats. Discard the threaded portion. Remove the remaining bit of swage from the barb by cutting along the axis 180 degrees opposite each other. Deburr the cut surface with a grinding wheel or file.

    Install a barb into each fitting and lockwire in place.
    [​IMG]
    The joint doesn't have to be horribly strong, all we're trying to do is keep the joints from coming apart.

    Install the long hoses to the Tee fitting. Lockwire in place.
    [​IMG]

    If you were smart and bought the proper barbed fitting to attach the tube to the check valve, good on yer. If you didn't, mix up some fuel-resistant epoxy and apply it to the stub of hose you're using to fit in the check valve. I used some from a fuel tank repair kit, the directions state it will cure while immersed in gasoline. Install the 6" section of tube over the remaining leg of the tee and the into the checkvalve. I used lockwire to first secure the hoses together and then to hold the hose on the check valve. I made a hole for the lockwire with a 1/8" drill.
    [​IMG]

    This is roughly where the assembly will sit.
    [​IMG]

    Poke two holes in the flange at the base of the filler neck, lockwire the checkvalve to the neck.
    [​IMG]

    [​IMG]

    This is good, but it isn't very stable. No worries, the 1150's canister valve provides a good place to add a strap.
    [​IMG]

    Now, with all that together, slip the legs down into the fuel tank. The left leg takes some snaking to get it to go behind the diverter plate in the 1150 tank, but it will go. The right leg falls into place.

    Work the filler neck back into place, even with the bulk of the checkvalve, it will go pretty easily.

    The whole project cost ~$50 and two hours of my morning.
    #1
  2. GS Addict

    GS Addict Pepperfool

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    This is how I did mine.
    The trick is to drill the hole in the filler neck far enough down so it does not interfere with the gas cap.
    Under $15
    Primes in less than 1 minute.



    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    #2
  3. Twilight Error

    Twilight Error Going nowhere slowly

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    Nice. That works too. How do you keep from losing the filler neck hose when the plug is out?
    #3
  4. GS Addict

    GS Addict Pepperfool

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    When the plug is out the hose is in your hand. The drilled hole is slightly larger than the tubing od so you have to make a point of pushing it back down.
    #4
  5. Twilight Error

    Twilight Error Going nowhere slowly

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    Gotcha.

    Yeah, easier and cheaper than mine, but I *am* a nuke, and we don't do anything if its cheap or easy...
    #5
  6. GS Addict

    GS Addict Pepperfool

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    I DO like your autoventing feature :D
    Beats tasting gas :eek1 :lol3
    #6
  7. bigjohn66

    bigjohn66 Been here awhile

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    When I had my 1150 I had a different take on this. I had thought about using the return fuel being sent back into the tank passing over an outlet connected to a pipe from the left lobe that would siphon the fuel like a perfume bottle sprayer. This would continually move fuel from the left side to the right with no thought from the rider. Seems it wouldn't be any harder to make than the above devices but might take a little R&D to figure out how big the hole has to be and exactly where to place it. As I didn't actually try this there may be technical reasons why it wouldn't work, such as siphons don't work when submerged or something like that. I don't know but it might be worth a try. For those who don't own an R1200 BMW used a turbine powered by the return fuel to move the fuel into the pump side of the tank. Maybe they knew something I didn't?
    #7
  8. Twilight Error

    Twilight Error Going nowhere slowly

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    The reason I didn't install a simple crossover from one lobe to the other was cost. By the time I had holes made, swarf cleaned out, bungs brazed/welded, repaint done... I'd have been in much deeper than I already was, and that doesn't buy fittings, hose or a QD.
    Similarly, installing another pump in the left lobe to feed the right would have been an expensive challenge.
    The siphon does not have to work when it's fully submerged, the liquid level in both lobes is even. When the fuel level drops below the hump, the right lobe drains and the left remains at the same level (barring slosh). If the siphon is primed, it links the lobes and allows the fuel to seek level. The check valve allows the siphon to prime automatically, which is only required if the siphon is broken because the tank has been run dry.
    #8
  9. bigjohn66

    bigjohn66 Been here awhile

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    My proposal was not for a gravity siphon, but rather one powered by the returning fuel flowing past a small opening and a single hose routed to the left side of the tank. It would work similar to the compressed air vacuum pumps sold to evacuate car air conditioner systems before charging. The flow of the returning fuel would create a vacuum over the opening and suck fuel into the right side of the tank. You would not have to modify the filler neck as the hose would just lay in the bottom of the tank. Once installed it would be self-priming and maintenance free. I don't have any way to draw a diagram now, but it would be pretty simple.
    #9
  10. GS Addict

    GS Addict Pepperfool

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    I think you are speaking of a venturi or jet pump.
    Yes, that would work but would keep more fuel on the right side than left after 1/2 a tank - not sure if you would feel that.
    The siphon is dead simple, cheap and I have had not had any problems with it ( installed for 10 years)
    #10
  11. bigjohn66

    bigjohn66 Been here awhile

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    Yup, I've called it a siphon but you've nailed it better with "venturi." I thought that was what you wanted though, fuel moved from the left side to the right where the pickup was.
    #11
  12. GS Addict

    GS Addict Pepperfool

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    Yes, that is what we want, but when we need it - at the bottom of the tank when the the right is empty.
    The system we have will maintain a balance at all times.
    #12
  13. Twilight Error

    Twilight Error Going nowhere slowly

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    That is the goal, yes. A venturi setup will do the same job, but it won't be as simple as a self-priming siphon. As far as feeling the weight of fuel in one lobe vs. the other, I haven't noticed it yet when the left lobe retained its load of fuel.
    #13
  14. GS Addict

    GS Addict Pepperfool

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    Good point
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  15. Bob

    Bob Formerly H20Pumper

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    Why 1/2 inch hose?
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  16. GS Addict

    GS Addict Pepperfool

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    i used 1/4"id Tygon
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  17. MikeWW

    MikeWW Motorcyclist

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    How much fuel is trapped on the left side?
    #17
  18. Mugwest

    Mugwest .

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    My fuel transfer technique is much cruder, admittedly, but it certainly works.

    First, orient the motorcycle into this position:

    [​IMG]


    You will hear the trapped fuel flowing from the left lobe of the tank to the right/pump side.

    When you are satisfied that all fuel has swapped sides, pick up the motorcycle using your favorite technique. It helps to have the bike in gear and the sidestand deployed.


    Good ideas and execution on the syphon approach, folks :thumb
    #18
  19. GS Addict

    GS Addict Pepperfool

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    "The Dr. Mugwest dirt nap fuel transfer procedure" :D:rofl
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  20. Twilight Error

    Twilight Error Going nowhere slowly

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    The output to the pressure regulator is 5/16 ID, so that was the minimum I wanted this hose to be. There was a larger selection of 1/2" bits available, and if I ended up needing to make a run to a hardware store for some unexpected part, it would be more likely to work. The 1/2" hose should flow enough fuel to keep pace with the pump as it drains the right lobe.
    #20