What type of welding for tank leaks?

[Texarican]

So, I'm learning the hard way.  I guess my bike sat so long it rusted from the inside.  The interior did not look that bad from what I could see with flashlight and mirror.  No signs of damage on the original factory paint (but scratches on top so I had planned a repaint)  Long story short, there were some pinhead sized holes that had apparently rusted through.  Once I finally filled the tank with gas, they showed up as paint blisters after a few days.  Now I've sanded back to bare metal to find them all and I want to fix them the right way.  They are small and sporadic with only 1 small area that has a 3 or 4 connected.  Nothing bigger than the head of a ball point pen.    

If I do this myself, do I need anything special?  I figure I'd rather go buy an inexpensive welder and practice on some scrap first than to pay somebody half as much to do it.  Will a small wire feed welder do it?  

[crzydood17]

welding is a lot harder than it looks... you might end up punching a hole right through... take it to a welding shop that knows what they are doing... have them fill the tank with a inert gas for safety and have them tack weld it up... simple and cheap... or buy a new tank which is preferable..

[jhutch2115]

I bought a  small proppane torch set and used silver solder to fill the holes after flushing out the tank real well using muriatic acid, then flushing with water several times. Then I filled the tank with warm water, leaving enough space for an air pocket. It worked great and no one got hurt! --Jim  

[gs500e]

Mayhaps i am totally wrong...

Since you already por-15'ed it, welding it will melt/destroy the por-15 in the area, and you won't be able to por-15 it again, and you will always have a trouble spot.  Pllus por-15 will contaminate the weld... it 'should' be removed before welding (welding would 'probably' work, as it would likely burn enough of the por-15 off to be able to make the weld, but...).

Dump more por-15 in it?

If it were mine i would have silver soldered/brazed the holes... and not used por-15 (or other one shot - hit or miss - cures).



Learning to weld, with an air-tight vessel as your first project = daunting.
I bet you would pull the trigger and make those pin holes into quarter+ sized holes.
My first 20 welding tasks with a welder, i was excited i got two pieces of metal to stick together (mig).
Thousands of welds later, i feel comfortable welding exhaust together (usually rusted piles of shazam and it's like welding rust, but i've done it enough times i can blow the rust away -- find clean metal -- and fill in).
I still would not attempt welding a thin metal rusty gas tank with a wire feed mig welder (possible, but not my idea of fun).  Which is why i would choose to silver solder it (minimal physical strength required, decent molecular bond for filling in) or braze it.
I would have a friend tig weld it if i 'needed' it welded.

That being said, i highly recommend buying yourself a welder of some sort.  I use a cheap Hobart (mig) i got from a welding shop (but is same one i could have gotten at home depot or some shazam (do yourself a favor and buy from a welding shop)).  Mine is only 50% duty cycle, but i'm not in a hurry anyway.  Get a bunch of 1/8" scrap pieces of steel when you buy it (probably free), and practice welding those.  
My first 'welding' was using an oxy/acetylene rig to replace floorboards in a 1976 VW Beetle (good steel-- brazing).  That floorboard was about the thickness of a gs gas tank, and was brand new.  I was blowing through that with oxy/acetylene (luckily it had that thick frame below it to soak up all the heat i was putting to it)... i can't imagine how bad i would have blown through it with a real welder as a first try, with no thick frame behind it.  BTW: oxy/acetylene is a much more versatile tool than a welder (i usually use oxy/acetylene to prep metal for welding in some way (heat cleaning, bend metal to shape, cut a decent hole so i can through-weld, etc.  Then i usually braze with oxy/acet unless i need the strength of a weld since i already have it out.).

[crzydood17]

i would just JB weld it if i was you... save the time and problems of welding... its gas proof water proof and can be sanded and painted....

[Texarican]

Well, I would not be completely learning to weld.  It's just been many years since I've done it.  I was actually once very good with a stick welder.  

 

Are there any success stories with JB Weld?  I'm skeptical.  

[crzydood17]

dude... JB weld has been used to fix cylinder heads and bores... Its just about gods greatest gift to man...

[the mole]

Sounds like going anywhere near yours with a welder will be like 'joining the dots'. There will be a relatively large area of very thin metal around each pinhole.
Its time for a good second hand tank IMHO. Or even a good cheap tank with a dent or two would be way less work to make good than repairing a rusty one.

[Texarican]

Sounds like going anywhere near yours with a welder will be like 'joining the dots'. There will be a relatively large area of very thin metal around each pinhole.
Its time for a good second hand tank IMHO. Or even a good cheap tank with a dent or two would be way less work to make good than repairing a rusty one.

I think you make a lot of sense here.  Unfortunately, even "cheap" tanks are not cheap.  I'm experimenting with the JB Weld right now but I consider it a band-aid solution.  Ultimately, I think I'll be tank shopping, keeping an eye on CL for something. 

[crzydood17]

that "bandaid" will last long after your dead lol :p and wont rust...

[Big Rich]

Or until the vibration rattles it off, the tank swells from pressure, or worst case the tank is involved in an accident. JB Weld is great stuff but it's brittle. It has to be 100% cured before gas touches it too.

I would run it with JB Weld on it, but keep an eye out for a replacement tank.

[crzydood17]

with the size of holes hes describing JB weld should be fine and expansion and contraction shouldn't be a issue... again... if it can repair cylinder walls i think it can patch tiny holes in a gas tank... theres other epoxy out there that is stronger... but it gets expensive, belzona is a insanely tough long lasting epoxy that basically liquid metal...

[Texarican]

Ok, the JB weld seems pretty good.  All holes were filled this morning and cured in the Texas heat all day.  I've got the 2nd color coat drying right now and the tank looks better than the first time around.  I'm going to give it several clear coats this time.  Should have plenty of curing time too since I figured out today some PO had apparently broken the tank petcock and glued a leak.  Got one on the way now. 

[slipperymongoose]

Welding a fuel tank is dangerous at the best of times, take it to the pro's, the metal of the tank is thin and if you dont know what your doing you will distort the metal and blow bigger holes, plus the fumes, at work they weld tanks by emptying them and pumping them full of CO2 gas but they are much thicker steel (diesel loco's).

[Texarican]

JB Weld did NOT work!  I drained the tank and let it air dry.  Then I used a very tiny nail to clean out the holes.  Cleaned that area down to the metal with acetone and let everything get good and dry before I used a credit card to press the JB Weld down into the holes.  Then smeared on a thick layer and let it all cure in the 90 degree garage for half a day.  Sanded down to where the JB weld in the holes was smooth with the surface and gave it a light coat of primer.  Then I put gas in the tank, enough to make sure the holes were covered.  I let that sit overnight, figuring if any gas was going to leak through, it would show readily in that light primer coat.  All looked good so I proceeded with color coats and eventually clear coats. 

Today, several of the holes started showing through and one actually began seeping gas.  On to plan B I guess.  I'll talk to some welding shops tomorrow.  If that does not pan out, I may be parting this bike out.  I'm already over my intended budget and with used tanks going for over $200, I can't see continuing.  The bike is probably worth much more in parts if I want to take the time to part it out. 

[crzydood17]

you cant take off all the jb weld and just leave the holes... gotta give it something to grab, if the weight of gas was enough to break through the horribly rusted tank then it would be enough to break out the super small surface area that is the wall of the tank. if you want to make the tank perfectly smooth with the JB still having a good contact patch, you can do 1 of 2 things... dent the area slightly around each hole so the jb weld can be like filler or dont sand all the way through leave a very thin layer of jb weld atleast 1 inch around the hole