Petrol tap question

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shaunstaples
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Petrol tap question

Post by shaunstaples »

Just wondered how much higher is the main tap to the reserve tap. I’ve got some 1/4 bsp taps with reducers down to 1/8” and was going to solder a bit of pipe into main tap but unsure how high to do it? What kind of height are they normally and what kind of range to expect?
Also bit of pipe in main tap should stop tap feeding off tank bottom?
My original ones look like they are 2 reserve taps with no pipe in tank as there is very little fuel in and they are both still running.
SPRIDDLER
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Re: Petrol tap question

Post by SPRIDDLER »

Both sides use the same tap (with filter) and rely on the trapped petrol in the left of the tank section for a reserve pint.
See page 37 in your Spares List here:

http://archives.jampot.dk/book/Spares_l ... _Twins.pdf
'There is a tide in the affairs of men
Which taken at the flood............'
shaunstaples
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Location: Sheffield

Re: Petrol tap question

Post by shaunstaples »

So opposite side of tank to whichever tap is favoured and what’s left is the height of the bridge at the back of the tank?
That’ll be why I’ve no reserve tap then 🙄
Thank you Neville
SPRIDDLER
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Re: Petrol tap question

Post by SPRIDDLER »

shaunstaples wrote: Mon Mar 27, 2023 8:05 pm So opposite side of tank to whichever tap is favoured and what’s left is the height of the bridge at the back of the tank?
Yep.
The Reserve is normally on the left.
It's said to be so that you can switch to Reserve without taking your hand off the throttle.
'There is a tide in the affairs of men
Which taken at the flood............'
shaunstaples
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Location: Sheffield

Re: Petrol tap question

Post by shaunstaples »

I had seen the arch over frame but not really thought about it, takes me back to when we had an old Francis Barnett as kids on a disused railway with the track removed. I remember us throwing it on its side to get every last drop! Happy Days

I would naturally use the R/H tap for main, but never knew why, "every day a school day"
thank you
g80csp11
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Re: Petrol tap question

Post by g80csp11 »

most pattern 1/4 BSP thread taps are available with or without reserve stand pipe
The filter normally unscrews so you can fit a stand pipe . its about 0.75"
They are fitted to later tanks

see ebay listing

https://www.ebay.co.uk/itm/294646115865
Groily
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Re: Petrol tap question

Post by Groily »

If you want you can even get 1/4 bsp ones with the reserve pipe AND filter with 'On Off Reserve' positions. Obviously more suitable for tanks with one tap only, but quite neat all the same.
So many choices . . . levers, plungers, extended plungers . . . 1/4 and 3/8 bsp . . . adapters to suit, T pieces, nipples and pipework . . . you name it . . . See for example:
https://www.classicbikepartscheshire.co ... l-taps-c86
shaunstaples
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Location: Sheffield

Re: Petrol tap question

Post by shaunstaples »

I've already bought the taps and filter, I was originally going to open the bosses to 1/4" for the choice of tap and better diameter filter and it was something Bill said about not having to drain the tank to clean the filter if it was external. So I got brass lever taps that were £10 each with no filters and then fit a decent filter that I can see through. The taps look ok and time will tell? They were advertised as 1/8" x 1/4" with 1/8" into tank, but when they came they have adapters and taps are 1/4" each end, disappointing but I'm not happy opening bosses in tank out to 1/4".
The filter is shiny and first one was poor quality, instantly failing my suck and finger vacuum test! When I stripped it down the centre 10mm threaded tube had so much slop in the thread into each end cap it just locked up when trying to tighten it. They sent me another and that passes my initial vacuum test...
I'll put 3/4" of pipe in the R/H tap adapter, so the tap is not feeding off the tank bottom and rely on the L/H side for reserve.
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MalcW
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Re: Petrol tap question

Post by MalcW »

SPRIDDLER wrote: Mon Mar 27, 2023 8:31 pm
shaunstaples wrote: Mon Mar 27, 2023 8:05 pm So opposite side of tank to whichever tap is favoured and what’s left is the height of the bridge at the back of the tank?
Yep.
The Reserve is normally on the left.
It's said to be so that you can switch to Reserve without taking your hand off the throttle.
Also, when you park using the sidestand you are slopping petrol into the reserve side rather than out of it.
Groily
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Re: Petrol tap question

Post by Groily »

Looks good to me Shaun, why not? If the threads in the tank hold up ok, all ought to be fine I reckon. I like your copper tubing - as long as there's enough flex in the 'coil' to prevent the sort of fracture some people say can happen? (I cheat and use modern rubber - yup, even with unsuitable markings on it shouting 'Not Period'. Don't care, it's ethanol proof and easy to get in modern bike emporia)

External filters make sense to me as I said - there are good reasons for having them if there's any suggestion of debris, rust, filler, sealant etc in the tank. There often is . . . and even 'clean' systems can clog the typical mesh filters on taps and carb entry banjos sometimes I have found. New tanks often being worse than old ones. Draining tanks and then having to find new washers for the tap-to-tank seal etc is boring.

On the reserve thing, I don't like letting things get that low to be honest, though it happens now and again. Much to be said for BIG tanks - my P11 regularly drove me mad with a 2 gal comp tank that wouldn't do a decent Sunday thrash from full in a world where fuel stations aren't two a penny, so I got a 3 gal one from the club . . .

Spriddler's side stand thing hadn't occurred to me - but 'yup, s'obvious now he says it!!

Good luck!
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