Any hints on fixing a petrol tank?

[liferocks]

Gidday all.
I've got a petrol tank thats been sitting outside (on the bike) for a few years and its pretty rusty. I've read up about it and about how to clean out the rust on the inside and how to solder cracks etc. (It hasn't had petrol in it so its pretty safe by now)
But my problem is that in one patch it has rusted right through, making a hole big enough to fit 3 or 4 fingers into, so i was wondering if this can be fixed by soldering too, or if i should block the hole with something and then solder it in place.
Any suggestions would be appreciated.
Nate

[Blakamin]

Whats it off? might be safer to throw it away and find a second hand one!

[laRIKin]

Yes you could solder a patch on.
I'm guessing that the hole is on the under side.
So the patch will not be seen.

I always fill the tank with water up to the point that I'm working on.(5-10mm)
This minimises the risk of an explosion.
It does mean that the last bit of soldering can be abit of a problem.
As the gases in the tank expand it will blow bubbles in the solder, in the last
bit you do.
So just let it cool abit and try again.
Petrol fumes are a funny thing, they do hang around for along time.
And nothing brings them back faster than a bit of heat.
So be care full.

Some guys I know were cutting up the petrol tanks at Lyttelton harbour.
They had bee open to the air and empty for a long time.
Up until the last cuts, the gas axes were still getting blowing out of their
hands. If they were cutting though any metal that had a over lap.
So treat the tank as a bomb, and you should be OK.
I would then get the tank lined with a plastic tank liner.
This will stop the rust and fill any hole you may have missed.
Also remember that, just because the tank does not leak with water.
Does not mean that it will not leak with petrol.
The molecules are smaller.

But as Blakamin said, it maybe time for a new second hand one.

Have fun, as it great to repair stuff and save money.

[Motu]

When soldering the metal has to be perfectly clean,that's a tough job on a rusty tank.We used to do that on car tanks,use a huge iron heated by a torch.But you are better off welding a patch on - I weld on the thicker metal and then maybe go over it with brazing rod,to fill in the gaps and do the bits that are too thin to weld.When finished use Por15 tankliner (get it from a paint supplier,not a bike shop)Fill the tank with exhaust fumes from a car tail pipe,keep the hose in and car running if you get scared,but I've found just a water flush then fill with exhaust fumes does the trick.

[liferocks]

Thanks guys, I'll have a go at cleaning it up real good then. Then see if its thick enough to weld and if not just solder it.
I was thinking that i'd put a liner in it anyway.
Its of an '86 gsxr400 (the model with the square headlight) and i've rung around and placed a few adds but can't find one anywhere.
Oh well, we'll see how it goes.

[vifferman]

I was thinking that i'd put a liner in it anyway.

If you get one of the tank fixing kits, it has three bottles: the first is just rust remover/neutraliser (basically orthophosphoric acid - same thing that gives coke its tang ), then you rinse that out with lotsa water; the second is acetone, which gets rid of the water then evaporates, and the third is the tank liner, which is basically a thick paint / plastic that uses acetone as a solvent. You can buy the liner on its own, and I reckon it's worth doing that and getting an extra bottle, as it's hard to get a decent thick coating all over with just one bottle. It's fairly viscous and hard to spread everywhere. Note that if you have any rust remaining, it WILL rust under the liner. And soldering will help to ensure you get a nice catalytic reactiongoing, and speed up the rusting process.
I had a VF500 with pinholes on the side opposite the fuel tap, where water would tend to sit and not get flushed out. I was very careful about it, but never quite got rid of one hole, despite several soldering attempts. I was trying to minimise the amount of destruction so the tank wouldn't need repainting.
If I had to do it again, I'd bite the bullet, and have it brazed, use two lots of tank prep, and repaint the tank. Do it once, do it right.

[Mongoose]

Thanks guys, I'll have a go at cleaning it up real good then. Then see if its thick enough to weld and if not just solder it.
I was thinking that i'd put a liner in it anyway.
Its of an '86 gsxr400 (the model with the square headlight) and i've rung around and placed a few adds but can't find one anywhere.
Oh well, we'll see how it goes.

Personally I would shy well away from a petrol tank with any hot flamey thing. As someone said, petrol gasses are a funny thing and lurk inside petrol tanks for ages and ages and ages.
Hot iron for soldering maybe, but no, nope, no hot flamey sparky thing for this kid, to much risk of BOOM! and up she went.

[kerryg]

Personally I would shy well away from a petrol tank with any hot flamey thing. As someone said, petrol gasses are a funny thing and lurk inside petrol tanks for ages and ages and ages.
Hot iron for soldering maybe, but no, nope, no hot flamey sparky thing for this kid, to much risk of BOOM! and up she went.

I had a very good result patching a petrol tank with the bog stuff that comes in a stick (you knead it to set of the curing reaction reaction). I got it at Repco and it literally sets like steel, and it sticks like s**t to a blanket. There are a few varieties of it so look for the one that says it can be used for petrol tank repairs. I can tell you from experience that ordinary bog lets petrol straight through.....

[vifferman]

I had a very good result patching a petrol tank with the bog stuff that comes in a stick (you knead it to set of the curing reaction reaction). I got it at Repco and it literally sets like steel, and it sticks like s**t to a blanket.

Yeah, it's a very solid epoxy. Jesse James used it one time on "Monster Garage" when some numbnuts didn't test a tank he'd welded up, and it pissed diesel everywhere when it was filled up.

[liferocks]

Cheers again guys.
I hadn't thought of that bog stuff, I'll have a look for some of that.
If it'll still rust under the liner how do you manage to get all the rust out, is that acid stuff that comes with the liner good enough?

[Motu]

Yeah,it's good stuff,will kill it dead,then you put in the liner.Actualy Jenolite is just as good.Heat the tank with a heat gun or hair dryer,this will get the last of the water out,then put the liner in when it's still warm.I got a litre tin I Por15 about 5 years ago,have used it heaps and have 1/3 left,much cheaper than buying the kit.

My XLV750 tank is the worst I have ever attempted to repair,they are not exactly falling out of trees.I had it acid dipped and it came back looking like a cheese grater,smashed in both sides,had been cut open and welded up in a couple of places to panel beat it into shape,big holes and pin holes everywhere.I patched the big stuff and tried to seal all the small holes with weld or brass - but evey time I put a torch near it rust would ping off the inside.Finally I got it to the point where it would just seep water out of half a dozen holes,then I put the liner in - Kream first,but it's very thick and didn't spread well,so did a second coat with Por 15.It's been in over 4 years with no leaks.Took a couple of goes to seal my TLR200 tank too.

[liferocks]

Awesome. Thanks Motu
Where did you get it acid dipped?
Or what acid did they use?

[vifferman]

Finally I got it to the point where it would just seep water out of half a dozen holes,then I put the liner in - Kream first,but it's very thick and didn't spread well,so did a second coat with Por 15.

Yeah, the Kreem is what I used, and it's hard to spread around. I reckon you could thin it with acetone, but if the Por15 works well, then why bother with the Kreem?

[Motu]

Awesome. Thanks Motu
Where did you get it acid dipped?
Or what acid did they use?

A furniture stripper could do it,but they don't like car and bike parts because of the oil and grease - but if you took it along and showed how clean it was they might let it in the tank.I think our local guy ''**** the Stripper'' has a problem with me personaly,he said no even before I opened my mouth.But close by is a crowd that does total immersion of complete car bodies,so it was no problem to drop it in a corner.

I'm a bit suspicious of this dipping,I have never seen a tank so rusty,it looked like it had spent all it's life out in a paddock,but when I took it off I didn't think it looked too bad,it's almost like they took it out of the tank and let it sit for a few weeks still soaked in acid (or alkali,whatever they use),but it was only a one or two day turnaround.I'd have to do a known good tank as a control.But if they dip complete vintage car bodies they'd soon have some angry customers if they rusted out after dipping.

[laRIKin]

A good trick for cleaning out your tank, is to put some nuts or chip (stones).
In your tank and shake the bejesahs out of it, but not so hard that you dent the tank.

And count the stones or nuts to make sure you get them all out.
And then flush the tank out well.