Explanation of How Petrol Tank Breather Works

[thunderbolt]

Can anyone explain to me how the breather works on the inside of the petrol tank? I know it is brazed into the bottom of the tank and then proceeds up inside the tank towards the filler neck where it enters a tubular circular part. On the other side of this tubular circular part where the small metal breather pipe enters there appears to be a pinhole (maybe a bit larger) to allow air to enter above the fuel level to enable atmospheric pressure to be present.

I want to seal the inside of the tank with POR15 sealant but am concerned the pinhole could become clogged as I run the sealant around the inside of the tank. The normal procedure to seal a tank is to rotate it around in all directions so all surfaces are covered with sealant. Is there a way to do this without clogging the breather hole in the top of the tank?

[Wicky]

Should be a vent hole in the filler cap area - make sure its plugged before lining the tank with sealer.

[8541Hawk]

The issue is not knowing the size of the internal vent hole.

If you had that info you could run a length of wire up through the vent while coating the tank and then remove it after the coating cures.

You could go by trial and error and try different size wire until you find what fits.

[popkat]

Tony mon posted a picture of the inside on a thread the other day (can't find it now though) it shows an internal breather hole, I think you'd have problems with Por15 as don't think you can get to this small hole without cutting the tank open.

[sirch345]

Tony mon posted a picture of the inside on a thread the other day (can't find it now though) it shows an internal breather hole, I think you'd have problems with Por15 as don't think you can get to this small hole without cutting the tank open.

Is this what you mean



Chris.

[popkat]

Tony mon posted a picture of the inside on a thread the other day (can't find it now though) it shows an internal breather hole, I think you'd have problems with Por15 as don't think you can get to this small hole without cutting the tank open.

Is this what you mean



Chris.

That's the one, the breather hole is the small one at the top just above the drain pipe, if you use Por15 it will probably seal that hole and the tank wont have a breather and you'll get fuel starvation, the picture I believe is of a cut open tank so you can see it.



.

[thunderbolt]

That's the one, the breather hole is the small one at the top just above the drain pipe, if you use Por15 it will probably seal that hole and the tank wont have a breather and you'll get fuel starvation, the picture I believe is of a cut open tank so you can see it.

Well, It looks like I am in Deep Sh*t then, doesn't it. My chances of sealing the inside of the tank and not covering that hole in are next to nothing.

Hey, Popkat do you by any chance live in Bideford, Nth Devon. If so I've been there many times. My wife was born in Appledore about 10kms away.

[popkat]

That's the one, the breather hole is the small one at the top just above the drain pipe, if you use Por15 it will probably seal that hole and the tank wont have a breather and you'll get fuel starvation, the picture I believe is of a cut open tank so you can see it.

Well, It looks like I am in Deep Sh*t then, doesn't it. My chances of sealing the inside of the tank and not covering that hole in are next to nothing.

Hey, Popkat do you by any chance live in Bideford, Nth Devon. If so I've been there many times. My wife was born in Appledore about 10kms away.

Yes, Appledore is just down the road, It full of holiday (second) homes and locals with 6 fingers and webbed feet .... Just a local in joke, hopefully your wife will see the funny side .North Devon, best part of the UK, but then I would say that

[macdee]

why not stick a drawing pin in it with a bit of tape over that
then take it off later, should be able to do it through the top of the tank
not matter if you miss that little bit

[macdee]

what are you using to clean the rust from the inside of the tank

[macdee]

me again

after looking at the vent again the bit of cut tank seems to be under the round channel does it vent the whole way round and the hole is just to let fuel run back into the tank

[thunderbolt]

why not stick a drawing pin in it with a bit of tape over that
then take it off later, should be able to do it through the top of the tank
not matter if you miss that little bit

That's a good thought Mac. I had planned to try and run the sealant around the roof of the tank and miss that part where the pin hole is as that is raised up a bit. But was worried that if some slopped around there and accidentally blocked it I would be riding with the fuel cap undone all the time.

[thunderbolt]

what are you using to clean the rust from the inside of the tank

I have purchased a POR 15 sealant kit which has 3 containers in it. 1 x 1 litre Marine Clean. 1 x 1 litre Metal Ready (acidic). 1 x 250 mls Tank Sealer.

Marine Clean cleans varnish and rust out of the tank. Metal Ready makes the tank surface acidic and removes more rust so the sealer will bond well to the inside of the tank.

Hope this helps. If you would like more info message me and I will scan the directions and send therm to you.

[popkat]

Por15 uses i think muriatic acid, if your not painting your tank be very careful as it will ruin the paint if it splashes. I just did my tank with Phosphoric acid, it doesn't line the tank but does leave a fine coating to help, i filled with fuel asap and it seems fine so far.

[nt1980]

Muriatic acid is Hydrochloric acid same as they would use in a swimming pool to reduce ph you can get different strengths but this stuff is lethal it melts anything after time. Phosphoric acid would be a better option as it will help with the rust unlike the latter imho