Topic: Welding Gas Tank

[Ernest T]

The tank on my CB400F was pretty beat up, a big dent on top where the tank bends down to meet the seat and something fell on the gas cap and bent the tank down around the cap.  Other assorted sharp dents on all sides, not shallow big dents. but deep, sharp small dents. 

I didn't want to use a lot of bondo so I drilled holes in the tank and used a screw in slide hammer to get the dents out.  Now it's pretty straight and won't take nearly as much bondo as it would have, but I have 8 holes I need to weld up.

How do I go about it?  Can you fill it full of water and weld it that way or is that dangerous?  I have a tank lining kit from POR 15 which includes a cleaner and acid etch that should clean it out pretty good.  Di you think that would be safe?  I don't want to make a homemade bomb.

[lucky]

Do not weld on a gas tank PERIOD!!

I do not care how well you washed it out.

Oh,,,some people will say its ok because they got away with it or they just got eybrows and face singed.

Just do not do it.

[Ernest T]

Thanks for your concern, I'm concerned too!  However, I know that people repair gas tanks all the time so there has to be a safe way to do it.  I'm thinking of taking it to a radiator shop to get cleaned before I do anything.

[Raef]

Use a shop a shop vac or compressed air to keep constant air movement in the tank. Remove the petcock and place a compressed air air gun in the hole letting it vent through the gas cap hole. As long as there is air movement and exhaust excess fumes can't build up to explosive levels and you should be ok....

At least that's how I do it, water traps fumes and that will turn out bad.

Mark

[lone*X]

Guess everyone has their own opinion but welding on a gas tank can be done safely.  I know there was a similar thread recently and opinions went from how to do it, to you will kill yourself if you try.  Well there are lots of OSHA approved shops that do this all the time so I figured a little research might help.  It didn't take long with Google to find several.  Searching for "safely welding a gas tank"  came up with some interesting discussions, as well as the link I am including here.  This makes more sense and is easier to do than any method I have ever seen suggested, even some I have used successfully on hot rod tanks.  Basically, in the absence of oxygen, you don't get ignition:

http://www.continentalcarbonic.com/dryice/weld-tanks-with-dry-ice.php      Dry ICE is available at numerous stores in my area, including wally world. 

[Lostboy Steve]

bah humbug..... dude i powdercoated a 1969 z50 tank so if its safe in an oven it'll be fine welding. Good call on the por15 #$%* works awesome! Good Luck!

[racemx51]

Not sure how much of a welder you are but if the tank is bad enough.. Like it was on one of my own personal bikes I cut the whole tank off of the base of it and fixed everything so it was all straight then welded it back on.. Sounds like a lot of work but if your a pretty decent welder it really isnt that bad.. Anytime Ive ever made a tank for a bike also I have somewhat kept the base of the stock tank and just made what I wanted around that. Also works for me I guess..

[RFogelsong]

I recently fixed all the dents and painted my 550 tank.  I pulled the dents with a stud gun and had holes that needed closing and yeah, not a big deal at all.  Leave the petcock out and open the cap (if it's still on). 

Mine aired out for about 3 days before I did any work on it so it was mainly fine there.  You may see some small little flare ups if you have some vapor left, but noting that won't burn itself out in 2-3 seconds.  Mine didn't do that you should be fine (well ventilated shop, etc.)

Also, at least on the 550 tanks, be careful with your heat, the metal is thin and your puddle may fall through if you get it too hot.  It was a lot of "weld for 3 seconds wait a minute" when I did it.   

[Don R]

I have used methanol to wash out the gas then hot soapy water to wash out the methanol. Purge with argon, co2, tri-mix or what you have handy from your mig welder. Dry ice is a good idea too. I always reach around a corner with a hand torch to flash test it when i think it's ready. Then methanol to remove the water then gas.

[Ernest T]

Not sure how much of a welder you are but if the tank is bad enough.. Like it was on one of my own personal bikes I cut the whole tank off of the base of it and fixed everything so it was all straight then welded it back on.. Sounds like a lot of work but if your a pretty decent welder it really isnt that bad.. Anytime Ive ever made a tank for a bike also I have somewhat kept the base of the stock tank and just made what I wanted around that. Also works for me I guess..

Not sure how much of a welder you are but if the tank is bad enough.. Like it was on one of my own personal bikes I cut the whole tank off of the base of it and fixed everything so it was all straight then welded it back on.. Sounds like a lot of work but if your a pretty decent welder it really isnt that bad.. Anytime Ive ever made a tank for a bike also I have somewhat kept the base of the stock tank and just made what I wanted around that. Also works for me I guess..

Not much of a welder at all and the tank is in pretty good shape.  The dents were in the top which made it hard to get them out.  I don't think I'm up to completely rebilding a tank.

[Ernest T]

Thanks for the suggestions.  The tank has been sitting for six months without fuel and I washed it out with soap and warm water today.  I dried it for an hour with a heat gun set on high.  My normal method is to stick it in the oven at 200 degrees, but it didn't fit.  It got too hot for  me to pick it up and all the water is gone.  It doesn't have a lot of rust inside, just a little surface rust.  I plan to weld the holes up (I'm going with dry ice), then use POR15 Marine clean and metal ready,  I might use the maine clean before welding since it gets rid of the old fuel varnish. I don't think I need to line it as long I keep it full of fuel.

[lucky]

Use a shop a shop vac or compressed air to keep constant air movement in the tank. Remove the petcock and place a compressed air air gun in the hole letting it vent through the gas cap hole. As long as there is air movement and exhaust excess fumes can't build up to explosive levels and you should be ok....

At least that's how I do it, water traps fumes and that will turn out bad.

Mark

If you did that you will not be able to TIG weld it because the compressed air will blow away the welding gas.

[Raef]

Use a shop a shop vac or compressed air to keep constant air movement in the tank. Remove the petcock and place a compressed air air gun in the hole letting it vent through the gas cap hole. As long as there is air movement and exhaust excess fumes can't build up to explosive levels and you should be ok....

At least that's how I do it, water traps fumes and that will turn out bad.

Mark

If you did that you will not be able to TIG weld it because the compressed air will blow away the welding gas.

Actualy once you get the air adjusted correctly it creates a vacuum and draws the gas in, Losing the gas affects the mig more so than the tig, I generally do it with a torch anyway.

[orange550]

Yeah welding the tank is easy peasy. You could wash the tank like crazy, and then run a hose from an argon bottle into the tank. Let the argon flow sort of gently. But enough to keep the air inside the tank displaced with the argon. The braze it or tig it.

Actually, when I was a kid, I split a seam on the tank of my Arctic cat minibike. My dad filled the tank to the very top with gas, then brazed the leaky seam from the outside. The gas that dribbled out caught fire but that's it.

[frankist]

Yeah welding the tank is easy peasy. You could wash the tank like crazy, and then run a hose from an argon bottle into the tank. Let the argon flow sort of gently. But enough to keep the air inside the tank displaced with the argon. The braze it or tig it.

Actually, when I was a kid, I split a seam on the tank of my Arctic cat minibike. My dad filled the tank to the very top with gas, then brazed the leaky seam from the outside. The gas that dribbled out caught fire but that's it.

thats sounds ahah insane. i know gas wont explode in liquid form but its still pretty hair balls.

[Don R]

All I can say on behalf of the guys I know that have been burned. Don't ever do that. If you take every precaution there is, it's still hairy.

[Duke McDukiedook]

Yeah welding the tank is easy peasy. You could wash the tank like crazy, and then run a hose from an argon bottle into the tank. Let the argon flow sort of gently. But enough to keep the air inside the tank displaced with the argon. The braze it or tig it.

Actually, when I was a kid, I split a seam on the tank of my Arctic cat minibike. My dad filled the tank to the very top with gas, then brazed the leaky seam from the outside. The gas that dribbled out caught fire but that's it.

That is insane, that's all I have to say.

[beveldrive]

The tank from my K7 had been empty with the cap off for a month or two when I decided to cut out the crazy locking fuel flap and weld in a patch to mount the 'monza' cap. I washed it out with very hot water and detergent. Then rinsed with clean hot water. Left it in hte sun to dry , then got started. The result:



Cheers
Steve

[liPPy]

Best looking K7 / K8 tank ever.

The tank from my K7 had been empty with the cap off for a month or two when I decided to cut out the crazy locking fuel flap and weld in a patch to mount the 'monza' cap. I washed it out with very hot water and detergent. Then rinsed with clean hot water. Left it in hte sun to dry , then got started. The result:



Cheers
Steve

[Kong]

Fill the tank with water and then light up a butane torch and hold it at the gas fill hold as you dump the water out.  When all the water is out of the tank its ready to weld.  There will be no explosion, there will be no fire.  It only takes a minute or two.  This works equally well if you find you have to weld and old steel car gas tank, its where the method was taught to me just about 40 years ago.

[Kong]

PS - I really like that tank.  Its got great area for painting and nicely defined panels if you want to do elaborate graphics or just simple pin-striping on it.  Simple and sweet.

[beveldrive]

Thanks Kong,
yes the K7 tank is simplicity itself! Beautiful lines, once the flap is removed and smoooothed away. Here it is after paint..

[bollingball]

Do not weld on a gas tank PERIOD!!

I do not care how well you washed it out.

Oh,,,some people will say its ok because they got away with it or they just got eybrows and face singed.

Just do not do it.

Lucky: You sir are just respectively wrong. This is done everyday.

                                                    Ken

[Danno]

I have used all the above mentioned methods and they all work fine but my favorite and least nerve wracking is washing it out with detergent then rinsing it out and while rinsing using the torch to get rid of any fumes that are left one thing that I think everyone can agree on is there needs to be plenty of air circulation and never weld a tank with the cap closed