Need help with peanut gas tank.

Discussion in '2-Stroke Engines' started by john morrow, Sep 3, 2016.

  1. john morrow

    john morrow Member

    My gas tank is leaking around the studs. Is there a way to mount the tank without bolting it down?

  2. FurryOnTheInside

    FurryOnTheInside Active Member

    You can strap it to the top of a rear pannier rack.
    I refuse to put the stock tank on my build, or at least on the top tube. I am concerned that it could slice my anatomy in the event of a crash. I will probably get a plastic mini/midi bike tank instead.
  3. john morrow

    john morrow Member

    Thanks for the advice, my problem is my bike is a chopper style bike.
  4. V 35

    V 35 Member

    Those tanks are poorly built, and require some build up before installation . The studs may not have been welded correctly . Invert tank, and apply a bead of JB Weld Epoxy to bottom, where stud sticks through sheet metal . When installing, use a rubber washer on each stud, to cushion, and further seal it. Apply a thin coat of JB Weld to stitched seam, after epoxy cures, easily sands or files smooth . This makes tank safer, as it dulls sharp edge . After scuff sanding, I fill low spots with JB Weld applied thin, allowed 24 hours to cure, than sanded and primed / sanded to perfection Let primer shrink / cure for a week before final sanding . I've done both the P K and Grubee Tanks . The little PK tank does not hold much gas .
  5. john morrow

    john morrow Member

    Thanks for the info V 35
  6. Frankenstein

    Frankenstein Active Member

    I thought you went with the method I outlined in the other thread you made.

    V5 I highly suggest not using jb weld, it's not resistant enough.

    Use a product called seal all, if you want to keep the bolts then strip the paint off half an inch long from the tank end, use whatever methods you think is best, I use a rotary tool with a wire wheel attachment but it takes a while, aircraft paint thinner works too good on the painted threads, also mixing xanthan gum, acetone, and a tiny bit of water makes a nice paint stripping paste, put on area to remove paint in thick blobs, put plastic bag over area and seal with tape, come back in a couple hours and the paint nearly wipes off

    Remove a quarter sizes patch of paint from the tank around the studs.

    Seal-all adhesive it over in thin layers, allowing it to dry a few minutes between layers. Let it cure for 24 hours and feel free to use the studs. Drill a hole through the mounting bracket and into the frame, put a self tap sheet metal screw through the bracket into the frame, this prevents the tank from rotating and you can just snug the tank down rather than torquing the shit out of it, which is how most tank leaks start anyways.

    Good luck!
  7. john morrow

    john morrow Member

    Sorry for the mix up. I fixed my tank and it no longer leaks, when thanking for info I should have put fixed problem.
  8. Frankenstein

    Frankenstein Active Member

    No problem at all! I mainly replied in concern about the idea of jb weld, I've seen and experienced too many problems with the approach. Of course most attempts were not used with stripping the paint, unfortunately the paint used on all the tanks I have seen are NOT gasoline or oil resistant enough to act as an appropriate substrate to any sealants, adhesives, or epoxies.

    My own first attempts with seal-all were failures after a couple of days, the gas ended up dissolving the top etch of paint, effectively removing the sealant from the paint, and allowing gas to leak between the tank and sealant.

    What the paint is actually made of is beyond me, it's almost definitely not a powder coat since it can't stand up to plain old gas and oil, so leaving it in place is the second half of the problem.

    I find that jb weld, while being a great port and crank case fixer-uper, is poor at constant pure liquid gas contact sealing, and since the vibrations from the motor, even from well balanced ones, tend to crack the epoxy on these kind of stress points it just seems pointless to try to rely on it at a preventative measure.

    The seal-all when applied to a clean and gas/oil substrate is actually better because it remains flexible, so vibration cannot destroy the bond or seal, and since the bare metal isn't gas soluble nor the sealant, it actually becomes a perfect method to help this particular and popular problem amongst users.

    Rear rack mounting is also a very nice way to help the issue if you strap the tank down rather than using the mounting bolts, though, if using the strap down method (currently the wayy tank is held to my bike top tube via zip ties) it's probably best to use seal all on the appropriate areas after removing paint. These tanks might actually get only a quarter of the mile and 3 quarter wide quality control the motor's get. I highly doubt they even build the motor in the same place it gets painted. It probably gets tossed around a dozen times before being poorly packed in the ripping cardboard box they send you it in,so the welds are likely half broken by the time you get it.

    Basically go with what works, I know beyond any doubt that cutting the bolts off and sealing over plain metal works without any chances of a leak. You can slowly degrade the process depending on your needs, but not usong the appropriate sealant and leaving the paint is practically a guarantee that you will end up with leak problems in time, at least in my experience.

    Now if it comes to tuning a motor so it can beat a b-12 stealth craft from here to China, refer to jaguar, he, for all intensive purposes, did the work for us, as far as leaky stupid tanks, I did too much to go unnoticed. I know my system of angle aluminum basically glued to the tank isn't the best, I experienced a peeling problem here and there, but I know that the tank doesn't leak and I don't need to resort to using special treatments to fix it.

    I'm looking at methods for spot welding aluminum to steel effectively without creating weak points in the steel. If I can do that I would have a way of making a ready to sell product that can be relied on by anyone who used it.

    I've also considered using rivets with closed ends, since rivets have a natural resilience to vibrations, but the 100% sealing of that point from the outside worlds seems to be a bit difficult to get.

    My 3 cents.