Second gas tank to crack and leak

Discussion in 'Motorized Bicycle General Discussion' started by scribling, May 21, 2014.

  1. 2door

    2door Moderator
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    Overtightening the fasteners and/or hard mounting the tank is a sure prescription for the failures the OP has. Those little studs or the spot welds on the tank won't take too much torque. Trying to tighten them enough to hold the tank to a steel top tube without some way to cushion the tank and hold it in place is futile.

    With road shock and engine vibration that tank is going to slip and move if there isn't something there to help hold it. Something cushy and sticky between the tank and top tube is nearly essential. There have been several good suggestion posted in this thread.

    Tom
     
  2. crassius

    crassius Well-Known Member

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    after the first one cracked, I got smarter and none of the last 4 or 5 hundred have done it
     
  3. Greg58

    Greg58 Well-Known Member

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    What I use under the tank depends on the top tube contour, I have used 1/4 " conveyor belt on some thin rubber and silicone have worked also. I set the tank on the tube with the rubber as close to the clamps as possible, I like to then turn the bike upside down and use a caulking gun with silicone and fill the gaps between the tank and tube. This has been the best way yet to keep the tank where I want it.
     
    #23 Greg58, Jul 6, 2014
    Last edited: Jul 6, 2014
  4. crassius

    crassius Well-Known Member

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    yeah, if top tube isn't straight, I use rubber cement to stick pieces of inner tube together to make a straight place for the seats of the tank (right above where the studs are) to sit - then I use the double-sided tape and double nuts
     
  5. scribling

    scribling New Member

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    Really? KCvale, you haven't had this problem? I wish I could say the same. The tanks are typical Chinee crap. I've been getting them from a shop called Pistonbikes near me.

    The problem with my bike is that I have two top tubes, so I can either put my tank on crooked or, what I did with the last one, cut the back studs off at ~1/4" and fabricate a bracket with a bolt in the middle. This worked great, I thought, and then the front stud cracked.

    I bought the rear bookrack tank but it is all wrong. The rack and tank don't fit together well, and either configuration, filler to front or rear present problems. Filler and bung are on the same side of the tank so if I put the filler to the rear I have an outrageously long gas line that will stick out past the end of the fender and loop back around, and with the filler at the front the petcock hits the break caliper.

    I'm thinking of taking one (or all) of my broken tanks and having it welded, at least they (sort of) fit on the bike. Or, maybe mount a teardrop tank on the book rack ...
     
    #25 scribling, Jul 7, 2014
    Last edited: Jul 7, 2014
  6. KCvale

    KCvale Active Member

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    Actually I did break one loose one stud on one my very early builds come to think of it.
    I used JB Weld Marine on it, it resists gas as well as water.

    The trick is to isolate the tank from the frame with something that will allow you to snug it up good but not move unless hit which is actually a good thing, it's beats a dented tank if it falls over.

    That's easy here, I cut that hard grip off all my throttles and throw the stock grips away and use BMX style foam grips, with a little hot soapy water you can 'milk it' on to the throttle barrel.

    Anyway, I have leftover foam grip material and rubber cement a 3" long piece the width of the tank channel between each set of studs and snug the tank up.

    Of course you could always go with a back rack and mount the tank there like this Caddy...

    [​IMG]

    I had forgotten all about that pic.
    That has the coolest front basket ever.
    It's a dual handle shopping basket that locks on to the front mount when you put the handles down, and comes right off when you lift the handles up.

    Then of course you can go with an even a cooler 'beer keg' tank and mount it to your seat bolts like I did this Caddy.

    [​IMG]

    I had Coyote Tanks in Southern Arizona make that up for me, it was like $125.
    I had them weld tabs on it the width of the seats neck fastener and just used a couple of left over rag joint 3 hole semi-circle metal mounts to attach it to the seat.

    In short, there are many ways to carry fuel, just be creative ;-}
     
  7. scribling

    scribling New Member

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    Well, welding isn't really an option. They want $40 to fix a $25 tank ...
    I tried using the long bike rack tank but it's such crap metal inside I cannot stop it from rusting immediately after I clean it out. Sure enough, the filter or petcock got clogged and wouldn't flow.

    I don't think I'm getting near the mileage out of a tank as I should. I rode about 30 miles today and ran out of gas. My car gets better mileage than that!
     
  8. AssembleThis

    AssembleThis New Member

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    Sorry about your gas tank problems. Unfortunately if your installing those engine kit tanks, note they are paper thin. That metal should be at least three times thicker to pull on it with those studs. I had major concerns about my kit tank as well. So I spent a few weeks designing, fabricating and a couple weeks testing a rear tank harness. I realize its unorthodox, looks complicated but the up side, its safe, there is no metal touching the tank and I've had no problems with leaks. Total cost for the harness less than 3 dollars. With some imagination I'm sure the method could be used to mount a kit tank.
    https://www.youtube.com/watch?v=_w1OscgZi14&list=UUpr5gXoGzPrQM_DwdldhzqA
    .weld
     
  9. scribling

    scribling New Member

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    Re: Thrid, actually, gas tank to crack and leak

    I finally found a method that worked. I have two top bars on my bike so I inverted the brackets, drilled a hole in the middle and put a bolt through it. So now there's no torque on the tank studs at all.

    Also, I was able to salvage one of the cracked tanks. I ground/grinded the crap out of the cracks on the outside and JBWeleded both the inside studs area and the outside, generously, around the studs. It's been a few weeks now and all is well.

    I bought a rear tank from JMMotors, (I think it was) and the thing is total crap. Its so rusted inside that rust flakes clog the fuel filter. I tried cleaning it out but never got it clean enough to use. Also the thing is made totally backward. The filler cap goes toward the front and the bung toward the rear ... Really? That way the filler is under the seat and the bung is sticking out the back like a tiny tailpipe. If you mount it backward, the bung hits the brake caliper and the rack needs to be cut. Just dumb. In any configuration it won't work on my bike. Also, JMMotors was pretty good about shipping quickly but customer support is non-existent.
     
  10. woogie_man

    woogie_man New Member

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    Jb weld is working for me.
     
  11. Dave31

    Dave31 Moderator
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    I use two mounting brackets on my tank with a nut on top and bottom. That way when I tighten them the stress is between the brackets and not the studs.

    I run the top nut down a few threads then use the bottom nut to squeeze and tighten the brackets together giving me a nice solid mount.
     

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