Gas Tank Baffling???

Discussion in 'General Questions' started by PocketBiker, Mar 1, 2015.

  1. PocketBiker

    PocketBiker Member

    I'm getting ready to build a composite gas tank.... approximately 4" wide X 5" tall X 17" long. I've never ridden one of the motorized bikes and wonder how important it would be to put a baffle or two in, to separate the tank, into halves or thirds. Is the sloshing of gas noticeable, or a problem, I wondered. I was thinking, without one baffle behind the filler neck, when coming to an abrupt stop, is it possible for gas to try to spurt out of the cap? Now, I'm using the China Girl cap and I saw a report that gas did come out of his cap (which makes me wonder how normal that is?) But, I'll be starting my tank next week and any feedback concerning the importance or advantage of adding baffles in the tank would sure be greatly appreciated.... Even if you don't have an opinion about building baffles in the tank, I'd like to know if slashing is a problem in the "peanut tank" or any other tanks used for any of you motorized-bikers while riding...........??



  2. fattirejack

    fattirejack Member

    I do get some gas out of my cap, baffle by cap couldn't hurt. Build it how you think is best, baffles would give more strength to tank.
  3. troyg

    troyg Member

    With that amount of fuel sloshing isn't something that will effect ride, but I have heard it leaks a little.There are fuel resistant foam inserts, that perform two functions, stop sloshing and give you a visual fuel reading.
  4. PocketBiker

    PocketBiker Member

    Fuel tank foam

    That's really interesting, Troy!

    The very first thing that came up on my screen, concerning foam baffling, was a solution from SafeCrest Fuel Tank Foam. Apparently, you can buy 3" cubes for a reasonable $1.66/cube from Merlin Motorsports, but they are in England.

    This company is here in the U.S. and found on eBay for $10!

    What I like about it, is that, it is an after-build solution, non-abrasive insert, that can be reversed, if for some reason, I didn't like it.

    I'm really thrilled to know about this, because building baffles inside the tank may seem easy, but it gets complicated for this amateur. I'm really glad to know that baffling can be dealt with, at any time.

    Thanks Troy!


    Attached Files:

  5. Arty

    Arty Active Member

    I too get a small amount of fuel oozing out of the gas cap.
  6. PocketBiker

    PocketBiker Member

    Like they say...... "I know nothing of what I speak", but if the oozing bothers you, I'm guessing it can be eliminated for $10, as I have to believe the sloshing gas is the culprit! By the way, according to Safecrest (one of several manufacturers) the foam only displaces 1% of fuel. That seems fair.

    Troy, are you sure, the sloshing doesn't effect the ride, or are you just used to it? I'm just say'in... :thinking:

  7. Arty

    Arty Active Member

    Do you just keep stuffing those cubes into the tank through the filler neck till it's full?
  8. PocketBiker

    PocketBiker Member

    Well, we wouldn't have to completely fill the tank, but that's is the suggested use. I think they were designed to use in race cars as a safety feature. Then, the companies realized that they could capitalize on motorcycles with sloshy tanks...... We have the advantage of having such small tanks that it wouldn't take much foam to fill. This kit offered here is just perfect!! It fills 1 gallon of space for $10! My tank is exactly, 1 gallon! :devilish:
  9. Arty

    Arty Active Member

    That sounds really interesting.
  10. troyg

    troyg Member

    I personally don't use them.I'm a friction/GEBE user, as such my gas is always in a antifreeze container either between my legs at shin level (diamond frame), or behind and beneath me on my recumbent.I honestly can't tell any difference other than liquid weight.I'm a straight line flyer, so maybe hard/frequent slalom would tell different, but as a commuter, no diff.
  11. PocketBiker

    PocketBiker Member

    Oh, okay, so your fuel is at a very low point. Because my tank will only be 4-5" wide, there wouldn't be much side movement, but the tank is at a pretty high C.G. and about 17" long, so it seems like it might be more of a factor and maybe a good idea to keep the fore and aft movement down.

    I wrote the seller of the foam who is a landscaper by day and a 20 year bike racer by night. He said he fills the tank with the foam and has used the same foam for 5-7 years in tanks.... but he did say that he always mixes his gas and oil in a seperate jug. (not in the tank) This would be very inconvienient for me, so I think filling the tank, say....... 2/3ds with foam, might be a good comprimise helping to keep the fore and aft slosh down and still allow enough "slosh" to mix the fuel right in the tank. The cool thing is, you can always add or take away foam as desired.
  12. KCvale

    KCvale Motorized Bicycle Vendor

    I suggest yes, put a couple of baffles in, I just built a 17" long tank and at half full you can get a pretty good wave going in there.

    I was going to attach a couple of sheet metal paddles to the cross struts inside, and didn't.


    Just a couple of vertical separators that don't touch the bottom of the tank will keep the waves at bay, and you don't have a tank full of foam ;-}
  13. PocketBiker

    PocketBiker Member

    Prestone Power..........

    Oh yes, with that description, I remember your bike, very well.... Classic!!! Talk about an inexpensive solution for a gas tank! Good job! And, with that tank alone, you've got to put smiles on 1,000s of people's faces, as they are commuting to work. :grin5: That's really a big reason that I'm building my bike... a cool social dynamic.
  14. PocketBiker

    PocketBiker Member

    Baffle or Foam?

    Yes, though I like the concept of the foam, it does feel a bit strange.... 95% of the time, I can have the fuel already mixed in my garage, but that other 5% at the gas pump does concern me, just a little. ie. will the gas and oil really get mixed up well with the foam in the tank?? So, it sounds like you're not crazy about the foam idea.... :confused:

    I would definitely go for the foam, if my tank were finished without baffles, but of course, it's not, so I'll tell you about my original idea before I heard about the foam, that would be relatively simple. And, I'd like your opinion. (though, I think I already know what it is)

    If you can imagine my long, rectangular tank made out of fiberglass.... (before adding the Caswell sealer) I will be cutting a rectangular access hole in the top of the tank regardless of what I do (so I can get some internal nuts on a few things; petcock etc) That cut out piece will be almost the full width and about 6" long. After it's cut out, I can hang two baffles from that cut out piece. They would not touch the sides or bottom of the tank. Before glassing it back in the tank, I'll brush a small amount of Caswell on the hanging baffles and after glassing it back in place, the Caswell will seal that replaced piece on the inside.

    Okay, so what's the Verdict from you forum guys????? Foam or baffle????

    1) On one hand, you've got a more traditional baffle system where the gas is free to still slosh around a bit, but mixing the fuel at the pump would be "normal."

    2) Or, the foam solution, where the slosh would be eliminated almost 80% but mixing the fuel at the gas pump might be somewhat questionable.

    Do you think the oil would mix in the tank with the tank half full of foam?
  15. PocketBiker

    PocketBiker Member

    After chewing the pros and cons...... today....... (a lot of chewing) the decision is clear...... The foam in the tank makes mixing in the tank unrealistic. I'm not willing to deal with a separate mixing container, so, I will be epoxying in two (tried and true) "hanging baffles" and that will have to do.
  16. KCvale

    KCvale Motorized Bicycle Vendor

    That should do the trick, and don't bother trying to caswel anything beforehand, you can coat everything inside once it's completed by just rolling the tank around with the caswell in it.

    I question that foam for a 2-stroke mix anyway.
    I can see gas alone pass in and out of the pores easily, but I wonder about cold oil in the mix.
    It would be an interesting test to do in a jar.
  17. PocketBiker

    PocketBiker Member

    Right concept, wrong foam

    In order to use the foam concept for us 2-strokers, I visualize, not a closed foam like the grey foam sold above, but more of an extremely open-weave, scouring pad. Like 1/4"-3/8" space in the weave..... so the gas and oil can interact at the gas pump. More like this nylon scouring pad. Of course, the plastic would have to be 100% resistant to ethanol....(good luck) I'll let you try it in your tank first :detective:


    scouring pads.png
  18. PocketBiker

    PocketBiker Member

    Aluminum Baffle Box

    just looking at threads this morning while waking up with my French roast coffee and saw my old posted question and thought some of you might be interested in seeing the final solution to my original question. I am building my own epoxy/Caswell-lined tank, and ended up buying $10 worth of aluminum sheet 6" X 18" and building a box which will be pop rivited to the cut out "door" in my tank, then replaced and glassed back in.


    The box is sitting on top of the tank (the top 4X6 door has not yet been cut out), but as you can see, the baffle box will be positioned approximately in the center of the tank, mostly to keep gas from sloshing forward and aft. I'm hoping, it will also eliminate the tendency for gas to want to spurt out of my 1/16" self-drilled gas cap breather hole. The 1/2" lightening holes were drilled to assist the gas and oil mixing in the tank, at the pump. When the foam is melted out of the tank, the top door will be cut out and this baffle box will be pop-rivited to the underside of the door and the door will be epoxied/glassed back in place, ready for the Caswell sealer.


    The rest of my build can be seen on my build thread: Thanks for looking..... Jim
  19. battery

    battery Member

    I have been riding years with the peanut tank. Never noticed fuel sloshing. Didn't affect the ride all. The amount that leaks out of the cap at full tank is minimal. Not to cause a drip off the side of the tank. You could always add a second washer to help with nit getting gas residue on top of the tank.
  20. PocketBiker

    PocketBiker Member

    Good idea! I'll just throw my tank and baffle that I've worked on for a week, in the garbage and go back to your peanut tank. I really don't know why anyone would try to improve on the China kit.

    Thanks so much for your help!