thread size on gas taps.....

[MEHAVEY]

`Anyone know what the thread size is on the Commando gas taps coming off the tank?

 

[hursty]

Hi,

All mine are 1/4 BSP.

 

[L.A.B.]

= 1/4 "BSP" (also known as "Gas" thread)

Note that BSP is a parallel pipe thread, therefore 1/4" doesn't refer to thread diameter. http://www.britishfasteners.com/threads/bsp.html

 

[ILLF8ED]

The fastback tank has a larger thread...3/8" BSP with inserts to reduce back to 1/4" BSP. British Fasteners on the east coast has these tap sizes if you need to clean up the threads.

 

[Ron L]

The fastback tank has a larger thread...3/8" BSP with inserts to reduce back to 1/4" BSP. British Fasteners on the east coast has these tap sizes if you need to clean up the threads

Are you sure? I have three fastback tanks, two badge -type '68's and a NOS '71 and they all take the same petcock as my Roadster and Interstate tanks. No reducing inserts.

 

[ILLF8ED]

Hi Ron,

Check where the tap threads in. Should be a hex shape on the brass fitting the tap screws into. That fitting also can be unscrewed and has 3/8" BSPF threads. The reason I know is when I bought my fastback tank it was missing the inserts. I purchased a 3/8" tap to clean up the hole and added the fittings, gluing them in with locktite.

 

[Ron L]

Out of curiosity, I pulled the 3 original and 1 reproduction fastback tanks off the shelf and all 4 have 1/4 BSP fittings glassed in. No screw in adapters. Not a big deal either way, as you found you can use inserts.

 

[Danno]

I was looking for a petcock on fleabay earlier today and came across this tidbit: Don't know if it's true, but one website selling parts said the 1/4 BSP thread is the same as 3/8 American pipe thread. The female fittings under the tank are 1/2" diameter openings.

 

[ILLF8ED]

Hi Danno,

Just looked up 1/4" British Standard Pipe thread - 19 threads per inch while 3/8" American Standard Pipe thread is 18 TPI. They are not a match.

Sorry,

 

[batrider]

I think 1/2" - 20 is the closest to it and some say it will work in a pinch. I wouldn't. Definitely not 3/8" NPT which is huge. It is 1/4" BSPP (BSP parallel) as opposed to BSPT (BSP tapered). This is also called 1/4 Gas. Threads are 19 turns per inch and taps are available from McMaster-Carr in the US (p/n 8328A22 for $17.15). Their catalog explains all this. I bought one because I use it all the time with a number of tanks and bikes.

Russ