Possible concern with "new" partial project... gas tank fitting connection?

Discussion in 'Motorized Bicycle General Discussion' started by fabgear, Aug 2, 2013.

  1. fabgear

    fabgear New Member

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    Hi everyone,

    My first foray into putting together a motorized bike for some distraction from current things going on is the bike I bought as a partial project in a package deal, detaiped here:

    http://motorbicycling.com/showthread.php?t=49248

    I've been cleaning it up and rewiring the motor, igniton coil and the kill switch and I have my fuel line all set and 85% built with good pinch clamps on all connections, higher capacity (lawnmower) fuel filter and a simple lawnmower fuel cutoff valve all connected up. Purchased a new half gallon tank on Ebay, which arrived today. Unfortunately, when I opened it up this afternoon, I noticed the threaded connection on the tail of the gas tank but the threading has me baffled....

    I figured it would have had a threaded barbed connector included, but it didn't. Looking at it, the threading appears to have a compression thread (fine), but that wouldn't make sense and it doesn't appear to be 1/4" or 3/8" npt either.

    This is the "standard" ebay/ kit tank from what I can tell, and I'm hoping it's not some foreign metric connection that I'm going to have a probpem tracking down... I would think that others here have run into the same problem, so I'm hoping someone here might be able to help.

    Thanks,
    Jeff
     
  2. JustAnotherBozoOnABike

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    ...high man and welcome in the house and to the hobby.

    anyway, i'm new at this stuff myself but if i'm not mistaken the kits come with a threaded petcock/fuel filter that fits into that threaded hole in the bottom of your new tank, here is a link to a page that shows this petcock/filter combo, just scroll down a bit.

    ...and here is a link to a thread that shows another alternative.

    hope this helps, bozo
     
  3. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    The thread is 10 mm 1.0 on the China Girl kit tanks.
     
    #3 MotorBicycleRacing, Aug 2, 2013
    Last edited: Aug 2, 2013
  4. fabgear

    fabgear New Member

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    Hmm.... that's not good. Simce its not actually a tank I bought as part of a kit (I bought the tank on its own and had the rest already), I just assumed it came with a fitting that mated up with the common parts being used. Didn't even think about that one, but in my defense, my mind's been preoccupied.

    Will need to relook at the fitting coming off it now, see if either I can either retap it to work with a standard thread or ill just have to see if I can buy a matching petcock.
     
  5. 2door

    2door Moderator
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    Listen to the man. It is a machine thread, not a tapered NPT pipe thread. It needs a washer to seal.

    If you're careful you can run a 1/8" pipe tap into the threads and a standard NPT (National Pipe Thread) petcock will thread into it. The trick is to not run the tap in too deep.

    Your other option is to buy a petcock from a vendor who sells the Chinese kits. It still will require a gasket, typically the dime sized red one that comes in the kits, to seal the petcock against the tank.
    Do not rely on teflon tape or thread sealing compound for a leakproof seal. And please don't use any glue like JB Weld.

    Tom
     
    #5 2door, Aug 2, 2013
    Last edited: Aug 2, 2013
  6. crassius

    crassius Well-Known Member

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    NOTE: there seem to be 2 diff tanks sold with kits these days

    one has threads inside the tank outlet, the other has threads outside the outlet - the one with threads outside comes with a diff petcock that has a 'reserve' setting
     
  7. fabgear

    fabgear New Member

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    Shows how "with it" I am right now....didn't even look at that post well enough to see that it was relating to machine thread. Yes, non-tapering thread for fuel? Definitely a gasket if I were to use those outside threads.


    I should have no problem gently running a tap in there tomorrow and cut some 1/8" FNPT threads and run a threaded barb into it.

    I wouldn't even try to use JBWeld on those tapered threads, but I'd definitely either use the teflon or pipe compound on the threads just as a backup... unless you have another suggestion. Obviously, I don't want to risk my safety over a $10 "correct" petcock, but this isn't my real project bike, so id rather just use what I can here rather than sinking in more money than I have to.

    Thanks yet again,
    Jeff
     
  8. mapbike

    mapbike Active Member

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    Get you a tube of this at your local AutoZone or some other places may have it also, put this on the threads, screw the fitting into place and let set up over night, this stuff will last, gas and oil have no effect on it, I keep a tube in the shop always, it is a great sealer and a good contact cement type glue also. good stuff!

    http://www.amazon.com/Seal-All-380011-1-Ounce-Adhesive/dp/B0000AXYZG

    [​IMG]

    Map
    reddd
     
  9. xseler

    xseler Well-Known Member

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    If you use teflon tape, be sure to use the yellow tape. The white tape is not rated for petroleum products.

    Good luck!
     

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