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Weeping fuel fitting...sealant?

Discussion in 'The Garage' started by kawabunga, Feb 11, 2020.

  1. kawabunga

    kawabunga XS650 Addict

    Upon recently completing my build, the final step was to put fuel in it and fire it up. I discovered that my fuel hose barb fitting has a slight weep at the threads from the tank bung.
    I used a weld in bung, 1/4" NPT, and I'm using a 90º elbow 1/4" fuel fitting. Because it's a 90º bend, it has to be fitted in a specific direction. I had the bung placed in the tank properly prior to welding but the heat must have distorted things a bit and my placement was thrown off. I used a 1/4" NPT tap to try and get myself a little more turn to get the fitting in the proper direction, which that worked, but now I have a very slight weep of fuel from it. I cannot go any further in because of both direction of the fitting and clearance issues.
    Has anyone used some kind of sealant on fuel fitting/tank bung threads before? All I have at the moment is teflon tape for my air tools, but I don't think that plays well with fuel.
    Any suggestions?
  2. Machine

    Machine Race the wind Top Contributor

    I'll betcha if you were to wind cotton thread into the pipe threads before assembly that cotton thread would be enough to seal it ? Some petcock gaskets are fibrous. That's my thinking. And it's cheap and easy to try
    Jim likes this.
  3. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Teflon tape is fine. They make "gas" specific Teflon tape. but it's the same stuff just thicker and colored yellow so it's easy to see in the tool box. And the "gas" is natural gas.
    Jim likes this.
  4. kawabunga

    kawabunga XS650 Addict

    Machine, the bung and fitting do not have a mating surface other than the threads used to assemble, so I don't think there's a way to get a gasket in-between them.
    Screen Shot 2020-02-11 at 1.28.46 PM.png Screen Shot 2020-02-11 at 1.29.24 PM.png

    Gary, I'll give the tape a shot. I was afraid that fuel would eat it up and end up leaking anyway.
    Jim likes this.
  5. DogBunny

    DogBunny Motorcychologist Top Contributor

    Yes, you have to use pipe sealant or teflon tape. This is what I use -- actually I often use it and teflon tape together. Anyways, there is not a single "correct" orientation for threaded fittings. With sealant, they will seal anywhere within a 360 degree or greater tightening arc. Or more. An important added function of the sealant is that it acts as lubricant, allowing the fitting to be further screwed in than if sealant wasn't used and preventing galling. And, another important added function is that it prevents galvanic corrosion that occurs when dissimilar metals are in contact with each other.
    There really isn't very much pressure in a tank. With good sealant, the fittings usually don't have to be crazy-tight to seal.
    gggGary, timbeck, lakeview and 2 others like this.
  6. timbeck

    timbeck XS650 Junkie XS650.com Supporter

    Seal-All ?????

  7. XSLeo

    XSLeo XS650 Guru Top Contributor

    Seal All would be my suggestion. I have used it for years to seal gas leaks.
    timbeck and gggGary like this.
  8. rsor

    rsor Wanna do this again!

    Permatex fuel resistant gasket & flange sealant. Worked on my petcock screws. Part number 85420.
  9. fredintoon

    fredintoon Fred Hill, S'toon. Top Contributor

    Hi kawabunga,
    Teflon thread tape. it's proof against anything except Gamma radiation, works at way above boiling point
    AND it'll allow you to set your elbow to the angle you want.
    mrtwowheel, Greyandridin and gggGary like this.
  10. Team Junk

    Team Junk XS650 Junkie XS650.com Supporter Top Contributor

    mrtwowheel and gggGary like this.

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