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petrol tap

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In the NOC shop part no. SS14 C3 041323L is described as "Petrol tap: Lightweights only: 7/16 petrol tank thread - Use 1/8 BSP fittings: Lever type: All metal plated brass, New". I have bought one as my old push-pull tap continued to leak even with a new cork insert. The description is incorrect and has mislead me. I have found that the petrol tank thread is 1/8 BSP and the 7/16 thread is the one on the outlet. Unfortunately I have bought a Dowty washer that now won't fit the tank end of the tap and a 1/8 BSP spigot and nut that don't fit the outlet. The outlet thread od seems to be suitable for a nominal 7/16" thread but the TPI seems to be 19TPI according to my thread gauges. Does anyone know what this thread is so that I can buy the correct nut to clamp the spigot? Someone else must have bought one of these taps.

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I think both threads are BSP.   I bought a jubilee ewarts by mistake , unlike the Dommy taps it has 2 thread sizes.   I will look at it tomorrow.    To make them seal you have to use good quality corks with a very close fit,  soak in hot water  and lubricate with bar soap or  red rubber  silicone stiff grease.   One thread is 1/8th bsp and the other 7/16  with 19 tpi  ( I think!)  Don't know why they are called these sizes as  they don't measure anything like it.    I once converted Italian 10 mm tap holes  to 1/4 BSP and had to drill out the 10mm threads to do it.

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Robert,

BSP threads are sized on the nominal internal diameter of the pipe, so 1/8"  BSP is suitable for a pipe of 1/8" bore. I'll 0rder a 7/16 BSP nut and see if that fits. Thanks,

David

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Robert,

So I've found. I've bought the nut from the NOC shop labelled SS11 B3_7/16PTN/SPIG: "Spigot and nut : Lightweights only - 7/16 inch thread for petrol tap,New" hoping this is the one.

David 

I can't find that size anywhere so far.  Here's a useful site giving measurements in mm too. https://www.v-flowsolutions.co.uk/british-pipe-threads/ It shows how the thread tap diameter is much larger than the size would imply.  Convoluted eh?

It shows that only 1/4" and 3/8" have 19 t.p.i.  Of course the i.d. to which the size refers is that of a steel tube, not copper, so it bears little relationship to the actual thread size.  Wiki also has a comprehensive table of threads but I expect everyone has found these tables.

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You have got me thinking now  , going to HAVE to delve into the  morass thats my garage and find that  orriginal Jubillee Ewarts Main/ reserve  tap.  Its a good one,  perhaps someone would like to buy it.!.

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Recently purchased a new brass petrol tap for my Jubilee from parts. Started to leak (small leak) as soon as I put petrol in the tank. Looks like it needs new cork seals.

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I am following the fuel tap threads with interest as the tap in my newly purchased Jubilee leaks and as the image shows, the previous owner tried to seal it with some kind of shalak. My simple view is that it's the wrong tap!!!

Any thoughts or comments appreciated. 

Also be good to see what the tap SHOULD look like, so show us yer taps!

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 The  bottom thread is 19 tpi  but 7/16" OD  with a  bsp/gas thread form.   From a BSP perspective it appears to fall exactly between 1/8 and 1/4 BSP.    (but with the same bore as 1/8 bsp !!.  All very interesting!.  Can't imagine why they used such odd sizes.  If it were mine I would consider drilling and tapping the tank to !/4 bsp  so I could use the commonly availiable   taps with 1/4 bsp top and bottom.  ( if there is enough metal ! )   Or you could buy my spare correct  tap!!

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Hi IAN , If you want to see a similar tap  Britbikes have one on e_bay  item no 264661510050, right style and threads but only main suuply,no reserve.  The reserve type has a slightly longer plunger area and the knob is scripted with instructions  on use.  Like mine !

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Hi Ian, Your brass tap looks like an old mains gas tap used by plumbers I have one like it, but not on the bike. Peter.

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This is what I've uncovered this afternoon, I believe the tank fitting is 1/8 BSP  the other end, fitted to the tap, looks straight...

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Guys, not sure if this helps, but if you look at the picture I posted in the side panel thread you will see the correct fuel tap. The corks can be a real pain to stop leaking if they dry out. You need to keep them wet if you empty the tank for some reason. The taps that the Club sell look right.

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Hi Kev,  the tap shown in the "picture" in the side panel thread is the correct one , and the same as mine, however !!,  because its not a photo   the artist appears to have  drawn it  with  a bit  longer horizontal body than it has . Understandable  being that small. I don't think the club tap is correct. The description makes no sense (its not 7/16 tank thread) and you dont need any  1/8bsp fittings  (the Tank thread IS 1/8) . Also it does not mention reserve and  it should. Perhaps John Dunn who bought one can tell us? The club tap threads look ok so it may  work  as a main only but as whoever wrote it up obviously was not  very interested I would not trust it.  And it should be Chrome not brass.  Can I please have my  top nit picker / rivet counter  badge  now?.

Hi Robert. I'll contact the awards committee and see what we can do, but you might have to wait a while. Would you like the award in Chrome or brass? At least the picture shows that the tap isn't something also used on a 1923 steam train!

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White enamel to match my Dragon Rally Badges from the 1960's with a chrome surround and a pin clip  ,not too big mind !.

 

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