petcock size

Discussion in 'Motorized Bicycle General Discussion' started by Bob Mac 18704, Apr 10, 2011.

  1. Bob Mac 18704

    Bob Mac 18704 New Member

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    I need to order a bung for the tank i'm making for my bike. I want to use the sick bike parts petcock. I need to know what the thread size is. I'm almost certain it's 1/8 npt but need to know definitely before I order. thanks
     
  2. sportscarpat

    sportscarpat Bonneville Bomber the Salt Flat record breaker

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    Engine kit petcocks are 10mm x 1.0 thread pitch. An 1/8" npt petcock will also work. The sick bike parts petcock with the blue lever is a nice part.
     
  3. Black_Moons

    Black_Moons New Member

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    Stock I believe is a straight pipe thread. However 1/8" NPT (National pipe taper) threads have allways fit in my tanks without any problems (And I use heavy brass petcocks), just use some teflon tape over the petcock threads first.

    Some people mention chasing it with a 1/8" npt tap, but I havent really seen the need. Likey would be a little stronger...

    However i'll note that on the tanks I have been getting, the braze on the bung ALLWAYS cracks... Especialy when I go over any washboard terrian with my heavy brass petcock. (And sometimes additional brass hardware depending on what im testing)

    My solution? Add another 1/4lb worth of brass braze to the tank around the bung. I have gotten pertty good at it, leaves a nice smooth but large fillet.

    (Subnote: My MUCH MUCH older kits tank is 2x as thick metal, and the braze fillet on the bung is like 1/4" radius as opposed to the newer kits 1/16" radius fillet, That tank has never leaked.)
     

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