Second gas tank to crack and leak

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

  1. scribling

    scribling New Member

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    I just discovered the new tank I bought has now cracked and is leaking.
    I tried not to crank the mounts too tight but then it got loose. It didn't crack when I tightened it down, it cracked while riding.

    Does anyone know how I can mount a tank so it won't crack?
     
  2. Davezilla

    Davezilla New Member

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    The best way to mount these is to use some type of rubber padding under the tank so the vibrations from the engine and or flexing from the frams can't transfer into the tank.

    I used an old set of gel grips, cut out sections of the grip and then put my tank on and snugged down the bolts, if you tighten the bolts down too much they will stress where they're welded to the bottom of the tank, crack and leak so if you have problems with the nuts working their way loose, use a little bit of blue locktite to keep them in place.

    Good sources for rubber under padding for the tank are old grips (especially the gel type) sections of old inner tube, or foam grips, cut a slit down the grip and sit the tank on them, as with all grips, use a section in front, and another in the back of the tank.

    The tank only needs to be tight enough to where it won't slip and fall to the side and any type of rubber be it from an innertube or an old grip will further prevent it from slipping so you don't have to tighten the bolts as much.
    Also, use the Blue locktite or any other brand thread locker that's light or medium strength, the red locktite grips way too strong and you may twist off the stud trying to remove it later on.
     
  3. maniac57

    maniac57 Old, Fat, and still faster than you

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    I use old thick rubber handgrips slit and slipped over frame tube. Use a three or four inch chunk under each mount and don't tighten it down gorilla tight. The tank can still move if pushed hard. Just draw it down snug and don't flatten the rubber completely.
    A layer of good double sided tape under the grips and the tank will help keep it secure even better.
     
  4. soup325

    soup325 New Member

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    also, use some split/spring washers to keep it tight, without over torquing it.
     
  5. Davezilla

    Davezilla New Member

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    I like the idea of the double sided tape to hold the grips in place... Same here, I tighten mine just enough to where it stays put but if pushed on fairly hard it can still move.
     
  6. Davezilla

    Davezilla New Member

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    Another good idea... The locktite does a good job of keeping the nuts from backing off, but lock washers work well if no locktite is available
     
  7. 2door

    2door Moderator
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    I've posted this suggestion quite a few times. It always worked well for me. I use a product called 'glass setting tape. Automotive glass shops use it to seat window glass into the channels. It comes on a roll, is about two inches wide and is about 1/8" thick. It is a rubbery compound that can be moistened with a light solvent like WD-40. Before the solvent dries the tape gets gooey and after it dries it will act as an adhesive to keep the fuel tank in place without tightening the fasteners too much. Once set the tape will cushion the tank where it sits on the frame and it will hold it in place without slipping.
    If you need to remove the tank later it will peel off easily.

    Any auto glass shop will have it and if you ask nice they might just give you a foot of tape. That's all you'll need to mount one tank.

    Double sided tape is also a good idea. I've used it and I prefer the thicker type. It will conform better to any curvatures than the thin stuff. But it can be a challenge to get off because it usually leaves a sticky residue.

    Whatever, don't rely on the metal to metal clamps and overtightening the fasteners to hold the tank on. It's almost a sure thing that the studs will eventually leak if you do.

    Tom
     
  8. bairdco

    bairdco a guy who makes cool bikes

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    i've used a cut up innertube wrapped around the top tube, and nylock lock nuts instead of the stock hardware.
     
  9. Toothy

    Toothy New Member

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    I used heavy duty double sided tape and tightened just enough so it wouldn't move.
     
  10. Davezilla

    Davezilla New Member

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    Ok, I really like the idea about the window setting tape as the most important thing here is to get rid of the metal to metal contact, I can see where this stuff would give the tank just enough way to prevent it from following the frame when it flexes on heavy bumps and then from the vibrations transfered from the engine which can eventually wear out just about anything mounted directly to the frame without some kind of cushioning...
     
  11. GearNut

    GearNut Active Member

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    I use hot water pipe insulation.
    It will let the tank slip and rotate on the bar if it gets hit hard enough, but under everyday riding the tank is very secure.
     
  12. CTripps

    CTripps Active Member

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    I've used strips of rubber, cut from a mat that was once used in the back of a truck to supposedly help reduce the odds of the load travelling around, and either a bit of double sided tape (the stuff you get with a window film/draft seal kit, it's really thin) or a little bit of 'Gorilla' tape rolled over on itself 'sticky side out' to hold the rubber in place on the bottom of the tank. I find that a thin strip of rubber under the front and back fastener/bracket between it and the top tube often helps as well. In the case of a curved top bar (cruiser) I cut one end off of a rubber tie-down (pulled the S-hooks out, of course).. the thicker end the S-hook passed through shimmed the gap from the top tube's curve nicely.
     
  13. scribling

    scribling New Member

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    Problem solved! I found some nice thick padding and built a different sort of mount that works great. My problem was that I have two bars on the top so the tank had to fit over just one and the bolts were getting pulled inward. Not any more, now it's mounted over both with a straight pull on the bolts.

    Also, I figured I had nothing to lose by trying to seal the crack in the tank with liquid gasket. Seems to work great. No leaks yet.
     
  14. scribling

    scribling New Member

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    Well, the third tank broke too. Those teardrop tanks suck. I bought a rear rack tank but of course it doesn't fit right. Nothing ever works correctly with these bikes. It's like a test of engineering and tooling skills to see if you can get one of these bikes together and running.
    I decided to clean this tank out before using it ... OMG, was there a lot of crap in there. I used apple cider vinegar and let it sit for a day or two, twice. It's finally pretty clean now. I can't believe the crap that came out of this thing.
     
  15. 2door

    2door Moderator
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    Which is why we always suggest cleaning the tank before installing it and to use an in-line fuel filter. I've yet to see a clean kit tank. They come from the factory with rust, dirt and scale (no extra charge) so they must be cleaned before using them.

    Tom
     
  16. crassius

    crassius Well-Known Member

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    I use a bit of double-sided tape under them AND I never tighten them very much. Tighten just enough so they don't move, then double the nuts so they don't work loose.
     
  17. scribling

    scribling New Member

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    The last one that broke was too loose and rattling around, gas was flying out the fill cap ... I gave it a little tightening, took it out for a spin and it was leaking when I got back.
    I had folded up inner-tube under it. Maybe that caused constant elastic tension on the studs and broke the tank. IDK, but it seems to me they could do a better job ... come to think of it, they could do a better job on every single item on these bikes. There's no corner that isn't cut or material that could be cheaper. Grrrrr!
     
  18. GearNut

    GearNut Active Member

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    That is why the kits cost so little.
    Ya get what ya pay for....
     
  19. Davezilla

    Davezilla New Member

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    That's so true... There are better tanks out there but they definitely cost more... I was looking into this back when I built up my first kit and there are a lot of different 80's moped tanks that would fit but they're not cheap be it new or used.
    The best low cost tanks are those plastic pitbike tanks like for the Honda CRf50 which can be had for about $35 or so but some mods need to be done like adding brackets to the frame tube etc. Most the older moped tanks go for around $150 and up
     
  20. KCvale

    KCvale Well-Known Member

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    Where are you buying your tanks?

    I use Skyhawk kits with 2/3 gallon tanks from gasbike.net and just use some of the left over foam grip material from re-gripping the handlebars for under the tank and after 100+ builds yet to see this problem.
     

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