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Old 04-10-2011, 07:09 PM
Bob Mac 18704 Bob Mac 18704 is offline
Motorized Bicycle Elite Member
Join Date: Jan 2010
Location: penna.
Posts: 127
Cool petcock size

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
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Old 04-10-2011, 07:31 PM
sportscarpat's Avatar
sportscarpat sportscarpat is offline
Bonneville Bomber the Salt Flat record breaker
Join Date: Jun 2009
Location: california
Posts: 1,634
Default Re: petcock size

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.
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Old 04-11-2011, 11:17 AM
Black_Moons Black_Moons is offline
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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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