Topic: How to solder a gastank

[Raul CB750K1]

This is not regarded a sohc4 thus I post it in the open forum. My Suzuki GZ250 leaking gastank has no possible repair according to the shop manager. Of course that's not true, it's simply that they doesn't want to take the annoyance for such a low money the will make.


The leak is very small, not even dropping but staining all the underside of the tank. It comes from where then tank bottom is welded to the mounting bracket. It's welded by some points (you know what I mean, that scissor-like device that applies current and the two plates melt together).

I was planning to use a butane torch and some solder and weld the union, so even when the leak is in the inside it will not go outside. The drawback is that it is very dangerous, tank has to be thoroughfully cleaned and vented, and then again, and let it sit for one month or so. Even then the gases will still be dangerous. My plan is to insert the petcock back at soldering time and fill the tank with water, so it will neutralize the gases and will act also as a cooling agent for the paint. With a dremel I will remove the paint and then solder the union.

I also thought about using and adhesive, but the problem is that I couldn't find any that withstand hidrocarbons. Also, the solder will provide some mechanical strenght.

What do  you think about that?

[Chris Liston]

How about jbweld.  that should fill the pin hole just fine and its gas safe.

If it was welded at the factory why not just have a welder grind down the old welds and weld it back up again.  I'd get a second opinion.

[Terry in Australia]

G'Day Raul, that welding technique is "Spot Welding", I've got one in my workshop, it's a very useful tool. (unlike myself, ha ha!) To clean your tank out so it doesn't blow up like an Islamic rubber doll, drain it, then pour a little dish-washing detergent into it, and fill it with hot water. Swish it around so that the detergent-y water comes into contact with all interior surfaces, leave the hot water in it until it cools, then flush it with your garden hose until you get sick of it. You can do that a couple of times if you like for safety, but I only usually do it once, and have had no problems, and still have all my bits in the right places.

Although you can solder it (you'll have to do it with an empty tank, as the water will cool the metal and the solder won't melt) you'd be better off brazing it, I've had to repair a couple of suzy tanks due to cracking underneath, and I've brazed up holes in CB750 tanks too, solder is ok for filling little rust holes, but brazing, in my humble opinion, is a much better option. don't mig or arc weld it though, the metal is pretty thin, and you don't wanna go burning holes in it. (been there, done that!) I've heard good things about JB weld, (I'm using it to fill a big hole in some F2 crankcases as it's brilliant for patching aluminum) but I don't think it should be considered a permanent repair for a steel tank. Cheers, Terry.  

[bike54]

i agree with terry brazing is the way to go
as for making the tank safe connect a bit of ruber pipe to a car exhaust and put it in the tank then run the car for 5 mins thats the way the garages round me make car petrol tanks safe before repairing them

merv 

[Raul CB750K1]

Thanks for the advice. I also thought that if the tank was filled with water it would get most of the heat so the metal would not get the right temperature.

I'm a little confused about the english terms. MIG or arc are referred to welding with a transformer and an electrode, where the current melts the electrode that put's the material in the surfaces to joint together, isn't it?

Then soldering is with tin (like in electronics or plumbing), with an alloy of tin and lead. For big surfaces a soldering iron is not enough so you need a propane or butane torch, like in copper plumbing, isn't it?

So, what is brazing? Is the same than soldering but with silver alloy instead of tin alloy? It takes a oxiacetylene torch instead of a propane torch, isn't it? Furthermore, it needs a higher temperature so chances are that the paintjob will bubble or darken in the exposed part of the gastank, isn't it? (I don't care about the underside).

I new that MIG welding was too much for such a thin sheet metal, so I'm open to opinions.


Raul


P.S. Regarding the exhaust I also read something on the internet. As long as you need gas and oxygen to get an explosion, if you get rid of the oxygen there will be no combustion...

[Quail "Owner of the comfortable k8"]

After I this post you infidels will never listen to me.  I weld, braze and solder tanks.  I just take a wet rag and put some dry ice in it, tie it in a knot and toss it in the tank attached to a string.  When the co2 smoke starts rolling out the neck I start welding.    Remember the greatest danger is a little gas and 02 in an empty tank.  Terrys method is tried and true and brazing is the easiest.  You can braze with MAP gas.  I thought this one up myself years ago, I am here to type this.

You can trust me, Prasie be to Allah
 Terry Muhammad Quail

If this offends anyone send your response to my email directly, better yet drive to my house.

[Raul CB750K1]

Please only genuine advice wanted. I know some of you would like to see me getting an instant tan...


Anyway, what about my doubts between brazing-welding-soldering? Was I right on my assumptions?

Raul

[dusterdude]

many moons ago,my dad would braze with a torch and a wire coathanger.worked pretty good.of course you do need flux with that.

[eldar]

Well most any method is open for use really. You can arc very thin steel BUT you have to use a very thin, low amperage rod and have the power down and move fast. Takes a fair amount of skill though so the usually result is holes. Same with mig though if you do not use gas with mig, it is a little easier. Solder I do not think will have the strength to hold up for a long time but everyone has different experiences. Brazing is probably the safest for the metal but damn that gas is explosive! 

No matter what method you go with, that paint in that area will be gone.  One more thing with mig and arc, they weld aluminum those 2 ways so maybe follow procedure for aluminum welding.

[douglascoolgrey]

Raul:

Brazing, on the web: http://www.tpub.com/content/construction/14250/css/14250_122.htm

Soldering, Brazing, Brace Welding, and Wearfacing, on the web: http://www.tpub.com/content/construction/14250/css/14250_115.htm

A good radiator shop should be able to fix your tank for you. They will also purge the tank of gas. That said, I'm a little excited by the dry ice idea... sounds pretty cool. Then again, I've actually met someone who blew himself up welding a gas tank. He wasn't, how should I say, the smartest man I ever met.

[mrblasty]

I would second the notion about the radiator shop, if you don't have the technical skills with a welder be it oxy acetelyn or the mig process it easy to make a mess out the tank I worked a fairly severe dent on a newer Suzuki tank, the tank needed to be coated after I got done with it and the radiator shop coated it for whatever reason the poked a small hole in the bottom of the tank to drain the coating and brazed the hole In all They charged about $50.00 Couldn't tell what they would charge for just the brazing but it couldn't hurt to ask. 

[Raul CB750K1]

I've found a two-component epoxy resin that, according to the technical datasheet, is indicated to repair tanks or pipes used for flammable gas or liquids, without degassing. It's also very strong, so I think I'm going to try it. A dremel wire wheel to remove the paint, thorough clean and the sealer. I'll post when I'm done. Maybe it would be better to braze it, but if the sealer keeps the gas in I can live with it. I'm positive the radiator shop will do a terrific brazing, but I'm not so confident they won't scratch the paintjob.


Raul

[bike54]

hi raul
i think after using the epoxy i would use one of the tank coating kits as well better two much than not enough

merv 

[MikeDeB]

Hi Raul,  If you're going to do it yourself then I'd go with Terry's method of cleaning the tank then braze it.  Otherwise, take it to a radiator shop.  After it's brazed up use POR-15 to treat the inside.  That way you can be assured the tank won't leak and no rust will form on the inside.  Just my .02

[ElCheapo]

Gas tank epoxy patch usually works well for small pinholes. Seals the tiny amount of rust that is making the hole. Better yet no booming tan and no heat. We used to use this to repair all kinds of automotive gas tanks.

[Raul CB750K1]

Bump!! I repaired the gas tank yesterday. Haven't checked yet but I think it will be fine.

Instead of brazing I finally opted for the easy way and bought a two-component glue that, according to the manufacturer, withstands most gases and solvents, including hidrocarbons. It's composed of an epoxy tube and a small bottle of what seems to be metal particles. You just have to mix in no specific proportion. The more epoxy, the more fluid the mix is and the longer you can work with it. At 50-50, you have about 7 minutes to work with it.

I worked in small quantities. First, masked everything well. Then, with the dremel and the wire weel, removed the paint as much as I could. Then, cotton and alcohol to clean the surfaces well. And finally, application of the sealant. I´m going to let it cure for about 48 hours, much more than the manufacturer recommends, just to err on the safe side. I applied the sealant very fluid, so it helped to enter in the plates junction. Because of that, even when the sealant is hard, it is still sticky when touching with the bare fingers -because of the higher epoxy proportion- so I guess it takes longer. Furthermore, it's rainy here, so the humidity doesn't help to cure the sealant.


If it works I believe it is safer and quicker than brazing. The glue costed only 6 euro (about 8 bucks) and only used a small quantity. What I'm still wondering is where the heck did the gas leak...


Regards

Raul

[Terry in Australia]

Hmmnn, lotta work there Raul, I hope you actually applied it where it was leaking from though, you don't seem too confidant? Cheers, Terry.

[dusterdude]

now terry,why do you wanna poo poo on rauls project like that.

[bryanj]

Raul what you done should be ok but personally i would use a coating inside as well. Years ago i used a UK product called "petseal" all on its own in a leaking tank and it was still ok years later when i sold it. I think the nearest modern equivalent is the por-15 mentioned already. Frost Restoration in UK sell it and they have a superb reputation to uphold.

[Bob Wessner]

Somewhat along the same lines, bike fuel tanks are subjected to a good deal of vibration and some flexing. I guess I too would be concerned about how well some epoxy might bind/hold at all points under these conditions.

[Raul CB750K1]

Terry, I actually epoxied every seam, so there is no possible leak now.The welding looks fine. I guess that maybe, as the sheet metal is so thin, if the welder kept it just a moment too long, was enough to develop the leak. It was a weird leak, no dropping. You could touch the underside and it was slightly wet, but the only leaking was through the tubes.

POR15 is, in my opinion, out of consideration this time. The tank is 4 years old, no rust whatsoever. The leak is due to the weld, so I had to seal it either from the inside or the outside. The epoxy is still curing, but I will keep posted wether it worked or not.

This epoxy have metallic strenght. You can file it, sand it, pain it, and according to the manufacturer, is not affected by solvents nor gasoline. Let's give it a chance...


Thanks for your advice buddies

Raul



P.S. I tried with Vegemite first but it was no good for sealing...n

[Terry in Australia]

I tried with Vegemite first but it was no good for sealing...n

You silly bugger Raul, I said to rub the vegemite in your eyes so you wouldn't need to wear welding goggles! Man, where did I put my English/Spanish translator again? Ha ha, Cheers, Terry.