Broke another gas tank!

Discussion in 'Motorized Bicycle General Discussion' started by Cylon, Mar 14, 2016.

  1. Cylon

    Cylon Member

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    Hey all, went for a trip that was about 25 miles yesterday with my fiance and I broke another gas tank :( (3rd one in about 2 years)

    They seem to always crack at one of the bolts on the bottom of the tank because my top rail of my frame is slightly curved it puts a lot of stress on those bolts. That and the mount it came with isn't the best.

    So far my solution has been to reinforce the bolts with JB Weld, wait the cure time. Then I'm going to coat around the bolt again and on top of the JB weld with Seal-All. This has been working on one of my spare bikes for about 3 weeks with no gas leaks. But, I don't really ride this bike, its a spare bike, so I'm not 100%. I'll post pix when I finish the tank for my main bike.

    Also anyone know where to get cheap rear rims with the 7 gears already on them? I have broke a couple of these too and have no more spares to repair another bike I have. Currently 3 out of 4 are my bikes are needing parts I've broke to ride again.
    [​IMG]

    [​IMG]
     
    #1 Cylon, Mar 14, 2016
    Last edited: Mar 16, 2016
  2. Chaz

    Chaz Active Member

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    I've done the jb weld fix and it works pretty well, but it's just a matter of time before it gives out. It's far better to do the jb weld on a new tank to prevent the issue. Also, I use velcro to attach the tank to the bar and then I don't have to tighten the bolts so much. The velcro and looser bolts also allows a bit of give when I bang my knee into the tank.
     
  3. Cylon

    Cylon Member

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    Yeah I had velcro on there and it worked great when I went to take off the broken tank I really needed to pull hard on it. I even needed to use pliers to take it off the tank.

    I put the JB weld to the old tank and I had a brand new tank in my shed so I put JB weld on that one when I wake up later today Im going to put the seal all on next then bolt the new tank up to the bike and keep the old one for a spare for when the next tank breaks.
    .wee.
     
  4. Chaz

    Chaz Active Member

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    Always good to have spares around. I think the preventative jb should do the job really well, you shouldn't have a problem anymore.
     
  5. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    I know how looks for a motor bike, may have one not think this is the greatest idea, unless it can be done sort of inconspicuously. This being, the way I mounted a plain but brand new plastic lawn mower gas tank.

    It is not the plastic or the lawn mower tank, but the brackets I made to connect from the frame to the tank that was never intended on being on a bike frame.

    I had already welded flat pieces of metal to the top to the mid bars to add stregnth to the frame, and a few small holes in the flat metal for gas tank brackets were easy to construct.

    Without welding, I also attached brackets for other items to attach to the frame with seat post clamps. The steel ones you can remove the bolt and spread it to go onto the frame bars, then bend back and bolt back in place. Don't expect to remove and reinstall the seat post clamp but maybe twice, or it will have metal fatigue.

    Other ways to connect to the frame with some other kind of clamp and use brackets so those brackets can line up perfect with the gas tank you choose can remove undo stress. The plastic tank I don't have a lot of capacity, but the idea of connecting to the frame by using adapter brackets may be useful.

    MT
     
  6. Greg58

    Greg58 Well-Known Member

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    One thing that works for me is silicone, I mount the tank and tighten it slightly then turn the bike upside down and use a caulking gun with clear rtv and fill the voids along the sides of the bar. The silicone flows between the tank and bar and keeps it tight. I leave the bike upside down at least a day.
     
  7. allen standley

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    Also anyone know where to get cheap rear rims with the 7 gears already on them?

    See Wes on 6th street. He got lotsa wheels.
     
  8. Cylon

    Cylon Member

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    Sweet thanks!
     
  9. Cylon

    Cylon Member

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    I went ahead and posted pictures so you can see what I did its super solid now
     
  10. 2door

    2door Moderator
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    You're overtightening the tank mounting studs. You are relying on them to keep the tank stationary and that usually results in tank failure. JB Weld, (glue) won't keep the same thing from happening again. And probably won't keep it from leaking again.

    Take some of the advice offered and find something that will keep the tank in place and only use the kit straps/studs and nuts to act as back-up. Unless the tank is held with an alternative method, trying to keep it in place by tightening the nuts on the studs will result in stud/tank failure from vibration and shock.

    Unlike the engine which should be mounted solidly to the frame, the tank needs to be isolated from the frame with something that absorbs the vibrations. There are many methods. Silicone, rubber, Velcro, thick double sided tape, etc. Whatever, don't rely on the studs to do all the work.

    Tom
     
  11. sbest

    sbest Member

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    My rear wheel bearing just failed.
    Bike shope replaced the bearing, used HD grease, tightened and trued spokes.
    $24cdn, about $19us

    Coming from motorcycles, ATVs and 4x4 trucks, I LOVE BICYCLES.

    Steve
     
  12. Dave31

    Dave31 Moderator
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    I use four fuel tank straps, and eight nuts instead of just the two provided straps and four nuts in the kits.

    Run the (four) nuts on your studs first, then two of the straps. Then mount your tank, use the two other two straps on the bottom of the top bar. Now you have straps on the top of the top bar and bottom.

    Now tightening the bottom strap nuts and the top strap nuts you will sandwich the straps tight around your top bar.

    Now you are still adding stress to the studs but you are not pulling on the studs causing so many leaks at the weak point at the tank.
     
    #12 Dave31, Mar 16, 2016
    Last edited: Mar 16, 2016
  13. Cylon

    Cylon Member

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    I think the biggest problem is the fact that Im using the stock bracket for the tank and it only bolts up to about 1/4th of the stud, so its putting more stress on the tank because of the leverage, I got double sided tape from work and I'm going to use some new strapping for the mounts to get it bolted down further.
     
  14. crassius

    crassius Well-Known Member

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    as one tightens the tank, the straps bend toward the center - I always watch the holes in the straps so that I can see the point at which the outside of the hole first touches the threads of the stud - stop there, as any further tightening will bend the stud

    if that isn't tight enough to hold the tank, then apply double-sided tape under tank
     
  15. 2door

    2door Moderator
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  16. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    I would listen to 2door first. I have seen quite a few clever and low-stress ways to mount the kit tanks over the years.

    That said, and keep in mind that I have no idea how mechanically inclined you might be, there is also the solution of building your own tank. Problems with kit tanks and the way they fit different frame types (or DIDN'T fit, to be more accurate) was what prompted me to make my own. Mine was made from 14 gauge sheet aluminum, using a hand-made wood buck to help shape the sides. I brazed it together. The only opening on the bottom is the fuel line fitting. My tank hangs on the frame from bolts which come through the top from inside (with fender washers for decent support) and are thoroughly brazed up top. And the tank is lined. Even if I get a deep crack and it actually manages to go through the lining, which would be a good trick, it would still be at the top of the tank. Nothing's gonna leak out. And I used Nitril rubber under the straps anyway.
    Other forum members have made tanks from steel and fiberglass. I think I may have heard of a brass tank also. And more often than not, the home-made tanks are of far better quality and construction than the kit tanks. The builder has the power to make a tank as solid as he/she thinks it should be, so they often go for rock-solid.
     
    #16 Allen_Wrench, Mar 19, 2016
    Last edited: Mar 19, 2016

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