Adding a gas tank

Discussion in 'Rack Mounted Engines' started by shawnshank, Jul 28, 2009.

  1. shawnshank

    shawnshank Member

    I'm running a tanaka 40 cc GEBE setup and I'm thinking about adding an additional happy time style gas tank to supplement the one that came on the tanaka. Is there a way to add an additional tank while keeping the small tank that came on the tanaka?
    If you've already completed a similar modification and you wouldn't mind attaching some photos of it, I would appreciate it.

  2. 5-7HEAVEN

    5-7HEAVEN Guest

    Here's mine:


    Here's one story:

    Drill a hole at the top of the tank for a standard brass nipple. Be careful if you replace the Happy Time's filter. When my FRAM automotive filter runs empty it might take hours for the fuel to pass thru.

    The reserve tank will now fill the engine automatically via siphon action. The engine tank will fill past the vented cap, causing massive leaks. You can plug the cap with a self-tapping screw and the engine will now vent thru the Happy Time gas cap.

    Before I installed the reserve tank, I had to fill the engine tank every 10 miles. I did this by running the bike up a tree. Of course when I brought the bike to level ground, the fuel would leak thru the vented cap.

    No more problems when I installed the reserve tank. My fuel supply had tripled and now I fill the tank every three days.

    Did I mention that my Happy Time reserve tank feeds TWO engines?:jester:
    Last edited by a moderator: Jul 28, 2009
  3. graucho

    graucho Active Member

    Could modify a bag from wallyworld and hide a tank in it. Close to the engine hanging from the seat?

    Attached Files:

  4. Silvaire

    Silvaire Member

    You could add a Happy Time (aka Whizzer style) tank and retain your original Tanaka tank, but you must have gravity flow from the Happy tank to the Tanaka tank.

    With an additional tank feeding it, the Tanaka tank fuel cap must seal fully (not be vented, that is).
    Last edited: Jul 29, 2009
  5. shawnshank

    shawnshank Member

    I think the cap on the tanaka tank is fully sealed. I've over filled it before and nothing leaks out.
    What I'd like to do and what I need help with (if it's even possible) is to attach the fuel line from the added whizzer style tank to the engine while keeping and without modifying the tanaka fuel tank.
    I was wondering if this would work: Cut the tubing that comes from the tanaka fuel tank to the carb, install a brass "T" fitting and attach the fuel line going to the carb to one end, the fuel line coming from the tanaka tank to one end and the fuel line coming from the whizzer tank to the other and also install a petcock on the whizzer tank line so that I can switch between the tanaka fuel tank and the whizzer tank so that I can just switch over to the whizzer tank when the tanaka tank runs dry.
    What I'm curious about though is the primer bulb and how that would be affected by such a modification. Would I be able to prime the engine from the whizzer tank if the tanaka tank runs dry?
    Does the whizzer tank require a ventless cap?
    Last edited: Jul 29, 2009
  6. 5-7HEAVEN

    5-7HEAVEN Guest

    You could also run the fuel line through the fuel grommet. That'd be better than tee-fitting the existing feed line.:idea:

    The carb's bulb will still suck gas from the primary tank, but passive siphoning action will draw fuel from the reserve.:detective:

    My engines vent through the keyhole in the Happy Time reserve tank. You could also make a vent hole with a very small drill bit.:idea:
  7. shawnshank

    shawnshank Member

    I'm not sure what your referring to. What and where is the fuel grommet?

    I'm also not sure where the vent is on my engine. Does every engine have a vent?

    Your talking to a novice here :dunce: that's why I need pictures.

  8. Zev0

    Zev0 Member

    The Tanaka does NOT have to be gravity fed. I ran mine and the tank was below the Tanaka tank. With only the aux tank vented as the normal tank uses gas it will be sucked from the aux tank. Trust me, it works as many of us already do it that way.
  9. shawnshank

    shawnshank Member

    Can you show me pictures of how you have yours set up??
  10. loquin

    loquin Active Member

    Does the Tanaka have 2 hoses from the carb to the tank now?

    If yes, one is the fuel line, and one is the fuel return line. The engine has a diaphram style fuel pump; it pumps more fuel than is needed, and the excess, along with enough air volume to replace the missing fuel is routed back to the tank.

    This means that any additional tank/fuel lines you add should
    1. Be a closed, airtight system, and
    2. have a fuel line 'loop' in the plumbing. Ref the attached sketch.

    Attached Files:

  11. Silvaire

    Silvaire Member


    I like your drawing.

    You show the return line going from the carb to the Whizzer tank. I think this would be the correct way to plumb things, and you would then NOT need gravity flow from the Whizzer tank to the Tanaka tank.

    With the Tanaka tank sealed, suction from the carb would then suck fuel from the Whizzer tank via the Tanaka tank. Only if the Whizzer tank is vented (and with the return line going to the Tanaka tank) would it need to be higher than the Tanaka tank. If both tanks were sealed it wouldn't matter which tank was higher as long as the suction was from one tank and the return to the other tank.

    With it set up as per Lou's drawing, I believe that ZevO is absolutely correct, and that you would not need gravity flow for any part of the system. For some dumb reason I was thinking vented cap and float type carb...
    Last edited: Jul 29, 2009
  12. Zev0

    Zev0 Member

    Ok, I don't have a picture at the moment nor am I any good at drawing, but here's how we do it. We seal off the cap on the main tank, run a hose from the aux tank into the top/side/whereever through a gromlet. Both hoses from the tanaka carb still run into the main tank. Don't know if you can grasp what I'm saying, but there's a lot of us that run it this way. BTW it works the same on a Robin/Subaru.
  13. augidog

    augidog Banned

    Last edited: Jul 29, 2009
  14. Silvaire

    Silvaire Member


    I believe that understand how you have your system plumbed up, but I don't see how it could work.

    If both fuel lines from the carb go to the original Tanaka tank (which is sealed), and the aux tank is lower than the Tanaka tank, the only way I can see that it could work would be if the net effect of both the feed and return lines created a negative pressure within the Tanaka tank. Perhaps it does, or perhaps there is some other explanation that I haven't considered.

    One thing I've learned in life though, is that you can't argue with success...
  15. Zev0

    Zev0 Member

    Silvaire, all I know is that it works for me and many many others.
  16. augidog

    augidog Banned

    Silvaire, the above link describes the setup being discussed...the one everyone in town is using successfully...someone should bump it once in a while, or maybe the mods can find a better place for it?

    note: the 40 has a check-valve style vent instead of a breather-cap...this means it already has the extra hole needed, get it? take the check-valve out, get the appropriate grommet, move everything down one hole, add the aux line in the top hole.
    Last edited: Jul 29, 2009
  17. 5-7HEAVEN

    5-7HEAVEN Guest

    The fuel grommet is that black rubber fitting on the engine tank. That is where the two fuel lines enter the engine tank. it is usually located atop the engine tank.

    Every engine tank has a vent. Usually it's the gas cap that is vented.
  18. shawnshank

    shawnshank Member

    I just took a look at the owners manual. It has a vent on the top of the tank and two fuel lines.

    page 5 of the manual:

    Now people can refer to the numbered parts I need to modify if that helps.

    Last edited: Jul 30, 2009
  19. 5-7HEAVEN

    5-7HEAVEN Guest

    I installed a 4-liter Happy Time reserve tank to supplement my 1.5 liter goped tank. It has a petcock, inline fuel filter and line to feed the goped tank, which is mounted directly across my friction drive engine.

    Since the new goped tank was leaking profusely from the fuel grommet, I patched that hole and moved the fuel and return lines onto the top.

    Thennn, I drilled another hole atop to accept a 1/8 NPT 90-degree fitting and nipple. This connects to the reserve tank. I also installed a draincock on the g-tank.

    When I open the Happy Time petcock, natural siphoning action fills the goped tank to the brim in minutes.

    Now I can carry 186 ounces, which is almost 8 times the fuel supply on an engine tank, about one gallon, 3 pints and 10 ounces.
  20. uncle_punk13

    uncle_punk13 Guest

    I use this method as well on my 40cc Tanaka.
    If I use a non-vented cap on my R/S 4-stroke, can I plumb it wit the same method using the Auxiliary tank with vented cap ?