Auxiliary Fuel Tank for Diaphragm Carburetors

Discussion in 'Performance Mods' started by gone_fishin, Nov 30, 2007.

  1. gone_fishin

    gone_fishin Guest

    this isn't exactly "wild" but it does fall into the "when good isn't good enough" category :)

    i've gotten a few requests for details of my extra tank, & i apologise for slacking off :oops:

    this is being done with a GEBE/tanaka32 setup.

    so, here goes...i'm posting my pics for now, and will be composing the rest thru the afternoon. this is way easy for the layman, and i'll keep it simple. that's what this topic will be, a simple presentation using "drinking straw" terminology, not the place to discuss rocket-science :cool:
    Mvc-811f.jpg Mvc-816f.jpg
    __________________
    "....Get a bicycle. You will not regret it. If you live." - Mark Twain - May 10, 1884
     

  2. gone_fishin

    gone_fishin Guest

    let's start by looking at the fuel system.

    the diaphragm carby simply draws fuel by means of vacuum, so we're just looking at a drinking-straw in a glass of cola.

    tip: when you "prime" the system, forget about "how many times" you're supposed to push the bulb, it's about filling the system before starting. pump the bulb until you see the bypass/overflow full of fuel, no bubbles. give it another one to be sure. set your choke if needed. if your engine's a good starter, you've probably just learned how to get a "1st-pull" almost every time :)

    so, the "draw" comes thru the vent on the gascap, then thru the filter/pickup inside the main tank. there is always a draw on the fuel & the overflow is constantly going back into the main tank, that's how the carby always has fuel to use. we can use that constant draw :)

    now, all we're going to do is change the direction and length of the drinking straw.
     
  3. gone_fishin

    gone_fishin Guest

    changing directions is simple. i used a small 1/4" long sheet metal screw to plug the vent in the gascap. then i put a 3/8" hole in the side of the main tank, positioned as near the top as practical.

    on the add-on tank, i put a 3/8" hole at the top. the new vent, in my case, was a breeze to locate, some folks may just use another venting gascap.

    after that, it's two rubber grommets & some 1/8" ID fuel line. i chose clear line because i like to watch.

    i put about 1 1/2" of line into the top grommet and placed the grommet in the main tank aux. inlet.

    i put enough fuel line thru the other grommet to let the end dangle about 1" off the bottom of the tank. then i "screwed" a 1 1/2" piece of brass tubing on the end as a weight. i put the grommet in place. done :)

    for the best first run, top off the main tank, cap it tightly with the plugged cap. fill the aux. tank...start the engine...

    if everything's tight, you'll see an immediate draw on the new line :cool:
     
  4. azbill

    azbill Active Member

    nice neat approach ! :)
    you could probably use spray paint for vinyl/plastic on the jerry can to blend in with the bike a little
    cool idea none the less dude :D
     
  5. gone_fishin

    gone_fishin Guest

    ;)
    MVC-818F.JPG
    as soon as i have a warm day :)
    __________________
    "....Get a bicycle. You will not regret it. If you live." - Mark Twain - May 10, 1884
     
  6. Aux tank

    Thanx Augi. Your explination and pics with captions cleared things up.
    Bill:grin:
     
  7. gone_fishin

    gone_fishin Guest

    i'm glad it helped...i hope i didn't put anyone off with the simple-talk :???:

    i should mention: my system draws fuel thru a 3' line and lifts it 14" without a problem :)
    __________________
    "....Get a bicycle. You will not regret it. If you live." - Mark Twain - May 10, 1884
     
  8. OldPete

    OldPete Guest

    2 strokes will lift a higher head than the 4 strokes, just the nature of the beasts. Two pulses vs one per engine rotation of 720 degrees. (as per Denis at GEBE.)
     
  9. gone_fishin

    gone_fishin Guest

    thanks...my engine is a 2-stroke tanaka 32cc, for reference :)
     
  10. spad4me

    spad4me Member

  11. augidog

    augidog Banned

    that's perfect...nice link :cool:
     
  12. augidog

    augidog Banned

    Last edited: Jun 22, 2008
  13. Zev0

    Zev0 Member

    Hmmmm that tank might be my answer.
     
  14. DetonatorTuning

    DetonatorTuning Active Member

    ZevO,
    i have that tank and will likely end up using it sitting on an alum.angle clamped to the left mount leg for the counter balance effect.

    my current concern is how advisable si it to drill a hole for the upper/ center bolt thru the GEBE upright mount strap ? i've seen people do this for a torsion location, this wouldn't place that much stress there.

    i had dreamed up another fuel system but it's just more money and complexcity for just a couple oz. more fuel. not worth it.

    thanks,
    steve
     
  15. augidog

    augidog Banned

    just use a tiny hole in the center of the strap, and a self-tapping screw with washer to secure the tank. i bet the bottom can be secured with a zip-tie setup...maybe a layer of inner-tube would be a good idea to resist rubbing.
     
    Last edited: Jun 22, 2008
  16. DetonatorTuning

    DetonatorTuning Active Member

    that doesn't sound like much support augidog.

    i'll have to look at it more closely.

    thanks,
    steve
     
  17. augidog

    augidog Banned

    i'm going to be calling (trying, anyway) dave's about some other stuff, i'll see what kind of info i can get.
     
  18. DetonatorTuning

    DetonatorTuning Active Member

    i was thinking of using an angle and "u" clamping it to the support leg to get enough support to keep it from bouncing down.

    i guess you could just put a piece of flat stock in front and behind the leg and using the thru bolts that come with the tank clamp it together so that it rests on the top of the dropout assembly.

    just wondering if that would put the outlets of the tank too low for the carb to draw ?

    thanks,
    steve
     
  19. augidog

    augidog Banned

    after yer comment about mounting the tank, i was mentally engineering the same kinda thing...single screw at the top, strap straddling the bottom 2 holes and tied into the mount.

    as noted earlier, my 2-stroke will draw pretty far, 14"...i understand a 4-stroke may differ a bit.
     
    Last edited: Jun 22, 2008
  20. ozzyu812

    ozzyu812 Member

    The manufacturers of the style of engine surely know that this is a major complaint about their engines. Why don't they address this and make a larger tank available? As an option or to replace the existing tank. I understand that blow molds are expensive, but I bet 3/4 of the people that own these engines would replace their tank.
     
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