Thread: petcock size
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Old 04-11-2011, 11:17 AM
Black_Moons Black_Moons is offline
Motorized Bicycle Elite Member
Join Date: Oct 2010
Location: Canada, Bc
Posts: 207
Default Re: petcock size

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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