Welding steel motorcycle gas tank

[Troy Fab]

I bought a new steel gas tank the was made in tiawon, (did not know that when I bought it) I am having to reweld a lot of sections on it because of the poor quality welds. I am using a Lincoln 185 tig welder. I keep getting porosity in the welds and tiny crator holes. Some welds come out fine and other go bad. I managed to get it all welded up and was testing for leaks. The only leaks I had were where I mounted sight gage bungs. When I went to touch up the spots all the welds were crators and porosity. I was very stuctured while welding this tank up with cleaning (acetone) (wire brush, (stainless) and keeping the tip sharp. I used 1/16th tungston (red) and mig wire from my miller welder as filler. ( I even wipe each wire off with acetone). Argon gas. Machine set to 90 and using foot pedal trying to keep small welds. I seem to have this trouble a lot with other things?
I hope that is enough information for some feedback. Is it the filler wire, we use this at work and do not have problems.
Steve

[arc]

well if there is porosity in the weld already the tig will just drag it through the rest of the weld. the tig process has very little cleaning power, so u have to manually clean it(grind or other mechanical means). thats sad to heard about the poor welds on the tank, you buy something and have to redo it thats the way it seems to be going in the world mass produce with no quality.

[metal-doctor]

Just a thought but for those kind of jobs you may want to consider silver solder as a repair to seal that unit up. Flows easily at low melting temps,strong & easily sanded to finish. Will still have to clean up the bad weld before using it though.

[arc]

yeah silver solder is used often for this too i forgot all about that. just make sure u get it from a welding store with the flux on it not the low or lead free wire stuff. the only problem with the brazing options paint can be a problem (doesnt like to adhere some times). also for cleaning the welds out id use a die grinder with a small bit (works great)

[Troy Fab]

how about the wire

I was taught to just use mig wire? Do you think the porosity is from the metal or is it my welder? Or is it that where the pin hole was when I tried to weld over it without die grinding out?

[Laiky]

wouldn't silicon bronze work better? you can use it with the tig. Silver solder with a torch might cause too much warping.

[metal-doctor]

silver solder with a torch doesn't require very much heat. We fix these tanks tha are rusted on bottom quite regularily & warpage is not a problem. We did one last summer that we had to run about 5" of solder on the bottom seam & no warpage.

[arc]

the copper coat on the mig wire "could" be a problem but highly unlikely. it is most likely the pin hole in the weld. i would grind it out and weld it up just keep cleaning it till no more pin holes.

[ridesideways]

i found the easiest way to repair a gas tank is with jb-weld. it holds up perfectly against most solvents including gasoline.

[arc]

jbweld is "ok" for quick fixes but if you have it out and the equipment there why not weld it up.

[metal-doctor]

Have to agree that JB has it's place but would only be a quick fix & personally would like to see you have a good permanent fix while it's off the machine.

[Donald Branscom]

I just have to answer this post.
Something is missing.

When you buy a new motorcycle gas tank they are covered in oil or some kind of petroleum
product.
This is all over the inside and outside.

You cannot TIG weld when these contaminates are present.
You also said,
" I seem to have this trouble a lot with other things?"
The welding machine my not be set up correctly.
With a 3/32- 2% thoriated tungsten you will need about 150 amps.
The reason is that when you depress the foot pedal you are only using a small fraction of that power. 90 amps would not be enough. You must use pure Argon ,not a co2-Argon mix. Called 75/25 and is used for MIG welding.

You said you were welding fittings for a sight glass on the gas tank.
Were the fittings made of brass??? A brass and steel connection.
If so you you would have better results with silicon bronze filler wire.

JB Weld has no place on a gas tank.

IF you have the TIG welding machine and torch set up correctly, are using pure argon gas, and Mig filler wire you should have good results with clean metal.

I wonder if you are using inner shield filler wire? FCAW ???
It has a hollow core with flux inside .

[CODE4]

I just have to answer this post .

After 7 years?

[ryanjones2150]

Welding steel motorcycle gas tank

I'm not familiar with your application, but I do a bit of fab work here and there on some drag cars. Most of my jobs involve taking some old stuff and making it better. A lot of times the old, nasty metal gives me fits with porosity with the TIG torch and mild steel filler metal. An old timer gave me a tip a while back, he said try using 309 stainless rod when porosity is kicking your forth point of contact (old paratroopers know what that is). He was right. When you get the boiling weld puddle of porosity going and dab that 309 rod into it, the puddle smooths out and flows like butter. Probably not an X-ray quality weld, but by god it works and has moved up to one of my top five tid bits of old school tricks from those that have forgotten more about fab work than I'll ever know. I'm sure someone will bust my chops for posting this, but you're certainly not welding on the space shuttle here. Give it a try.

[old jupiter]

After 7 years?

Why not, Code4? If it was an interesting, informative thread then, why can't those of us who haven't seen it make some more comments and get more feedback and clarification? I've never understood why re-starting an old thread bothers some. Would you rather have old threads just deleted?