Petrol Tank / Tap connections

[flatdeck]

Hi, I have had ongoing problems with leaking petrol taps (push-pull type). I even bought new ones and have no luck getting them to seal. Now I am looking at replacing them them with lever type or something else. What I would like to know is the whether the thread I have on the tank for the taps to screw into is common or not. It is 3/8" with 28tpi. I am suspecting it is a "BSA" specific thread since I cannot find it on any charts anywhere, which is making it difficult to swop out. Dave 1949 A7 ST

[MG]

Hi flat!

The taps/mounting holes originally are 3/8 BSP.

I'm only using BAP taps, not the best looking, but work a treat. Here's some more info:
http://www.audioworld.net/BSA/forum/index.php/topic,2862.0.html

Cheers, Markus

[trevinoz]

Dave,
             If you persevere with the taps you have you should be able to make them seal.
I bought a new set from your well known supplier in N.Z. but had problems until I fitted new corks.
Good as gold now.
 If you buy the lever type as fitted to late bikes you may find that the rubber seal swells and chokes the tap.
A drill usually fixes this.
                                     Trev.

[chaterlea25]

Hi flatdeck
It seems there may be adaptors fitted to your tank, some times these hold a fine mesh filter sometimes not??
The fine thread you see on your tap is 1/8th BSP,  common enough to find
HTH
John O R

[LJ.]

Hi Dave... If you were still in the UK then B&Q have a good assortment of BSP fittings, there maybe a similar DIY store in NZ. Don't forget to use plenty of PTFE tape round those joints as well, it doe's help. I'm wondering if it is the corks that are not sealing?? a common problem I have found is dirt and rust dust in the petrol tank, movement eventually grinds it fine enough to pass the wire gauze filter then an accumulation in the cork barrel will wear away the corks themselves like a grinding paste. Cleanliness is important with cork taps. Hope you get to sorting the problem out. Cheers!

[RoadRunner]

Hi,
Apologies for jumping into this thread, but when joining up the petrol tap connrections/spigots is there anything else one should use apart from PTFE tape? Surprised PTFE tape isn't affected by petrol.

Cheers
RoadRunner

[MG]

I'm using Loctite 572 thread sealant, that stuff works a treat. I found that PTFE tape will dissolve in the petrol sold here.

Cheers, Markus

[LJ.]

What exactly is PTFE tape made from? Sounds like another product that will have to be replaced with something that is resistant to alcohol, if alcohol is affecting it that is. Seems like you guys in Europe with 10% alcohol are giving us in the UK a preview of what's to come. 

How about Boss white & hessian as used by plumbers in the old days?

[Brian]

I've been using Loctite Hydraulic thread sealant and have found it very good, so far nothing I have used it on has leaked.

Description:
569 Thread Sealant is a high strength anaerobic sealant, it resists high pressures and vibrational loosening, has excellent solvent resistance, cures on active metal surfaces when confined within threads of metal connections. 50 ml bottle.

[bikerbob]

Hi there.
I believe PTFE tape is Teflon based but you have different types of tape if you are using it on a gas joint you should use the type that has a yellow reel. It was originally designed for tapered threads if you have straight threads like fuel taps then it should not be neccessary you should use a sealing washer such as the Dowty type or Ewarts these can be bought very cheaply on Ebay.

[brackenfel]

Just a thought, they are leaking from the tank threads & not past the cork?

Recently I took my A10 tank off, drained most of the fuel out & left it to one side for a while.. When I put it back on the bike petrol p****d out of one of the taps. I guess this one was above the fuel line, as it was stored sloping (ie not level) fuel had covered one tap, the other dried out..
I tried soaking the cork part in fuel for a while but it still leaked a bit.. In the end I put the tank back on the bike, more fuel in the tank & put a drip tray full of tissue beneath the tap.. Eventually the drip stopped...

Cheers,
Adrian

[Goldy]

You have to be very careful here because some gas (BSP) threads are parallel and some are taper. If it,s taper then use thread tape or paste to seal, but if its parallel then it seals on the flange of the fitting with a fibre washer. I found two new old stock original Ewarts petrol taps at the Classic Bike show a few years ago. The guy wanted £30 for them, best thing I ever bought they are really good.  They are parallel and seal on the flange.

[1660bob]

OK here`s my smarty pants bit: PTFE is short for Poly-Tetra-Fluoro-Ethylene. No,I don`t know exactly what that means, but I do know that it is widely used in the chemical industry (or at least was in my early working days).Its main use is in the containment of some of the nastiest substances used in such industries because of its excellent resistance to chemical attack from such delightful liquids as Hydrofluoric acid/Nitric acid, both of which will happily eat through stainless steel, (and fingers....Hydrofluoric at high strength carries on burning flesh until the surgeons amputate....) (a bit like the monsters blood goes through the spacecraft floor in the Alien film- but perhaps not quite as fast !). Its (PTFE)used to line tanks/pipelines and for gaskets, pump gland seals etc and as we all know, its both pliable and slippery, giving us aerosols of "dry" lube for our cycle chains, and  good `ol PTFE plumbers tape, which is where its pliability gomes good, wrapped around threads and squelched into the thread roots when parts are tightened together, it lubes and seals the joint.Given a track record like that, i can`t see it being outfoxed by even by the latest substances that pass for petrol ........Perhaps its only fault now is its lack of thickness as a tape-it used to be much thicker and more substantial,microns thin nowadays,drops apart mechanically rather than chemically.Bob.

[A10Boy]

I have found that new or dry cork taps need soaking in petrol / parrafin for at least a week before use. They will be ok then.

I remember learning about the effects of hydrofluoric acid on flesh when at college. It really is nasty stuff, we were told that if you were unlucky enough to get some on a hand you will loose your hand. We didnt have to use it fortunately.

[BSA_54A10]

I have always soaked corks in warm ( not boiling hot ) water to swell them.
Once placed in the tap the petrol will stop them drying out
Never had any luck trying to soak cork in petrol.

Yes HF is fun stuff but just about the only thing that will dissolve silicon so vital to Al chem labs.
It also gets produced when molten aluminium comes in contact with the atmosphere.
Used to eat out the insulators in the bag house, quite a PIA

[bikerbob]

I used to use hydrofluric acid in a paste form it was only a 5% dilution it was used to clean the welds on stainless steel you applied with a brush then left for about 30 minutes then washed off if you did not use rubber gloves and got some on your fingers even if you washed off straight away the skin would turn yellow and eventually die but there was no lasting damage you just grew a new skin but that was only 5% solution any stronger and you would probably lose a finger or worse. Needless to say we were very careful using it but it did a great job cleaning the burn marks on stainless.