Will it catch fire?
Seasoned HDF Member
Joined: Mar 2008
Posts: 9,384
Likes: 1,776
From: Central Texas
Exhaust off of a car bike lawnmower or any gas engine is cheaper than nitrogen. Just run the exhaust into the gas tank until you can feel the gas tank is hot and the kaboom is gone. but in the long run you will probably be better off having it done by a pro.
Last edited by 6 gun; Feb 15, 2018 at 05:18 PM.
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,544
Likes: 6,419
From: Honah Lee
Fill it with water. I had a 60's tank fixed that had a crack in it years ago. One welder said no way. An old timers took one look and said no problem. He silver braized it full of water. Thoes fumes are dangerous. My son has a small machine shop and welding booth. He got some terrible burns doing what you want. As soon as he hit the arch, thoes fumes made a flash out the inlet. He got some third degree burns on his arm and neck. He said tank was dry.
These days, I probably would get another tank if all possible. You could be liable if something happens to someone else.
These days, I probably would get another tank if all possible. You could be liable if something happens to someone else.
Last edited by Jackie Paper; Feb 15, 2018 at 05:41 PM.
Seasoned HDF Member
Joined: Apr 2012
Posts: 9,980
Likes: 5,218
From: Michigan
A friend of mine said to always use a baking soda/water solution in the tank before attempting to weld.
Drained the tank when completed and flushed and rinse with fresh fuel before re-filling.
U can't be too careful when serious bodily injury is a possibility.
Drained the tank when completed and flushed and rinse with fresh fuel before re-filling.
U can't be too careful when serious bodily injury is a possibility.
Seasoned HDF Member
Joined: Sep 2009
Posts: 25,307
Likes: 2,443
From: Eastern NE
Do what my cousin did many moons ago w/their minibike gas tank. Use a lighter to look in the fill hole...we called him "hairless" for awhile. 
JK...don't do that...listen to others w/their advice.
JK...don't do that...listen to others w/their advice.
Seasoned HDF Member
Joined: Apr 2017
Posts: 9,604
Likes: 20,708
From: Globe AZ
personally I would not use water, as it can lead to tank rusting. as others have said, purge the tank with an inert gas (nitrogen, carbon dioxide, hell even argon) and keep the gas running while welding to prevent a flash. Fuel vapor needs oxygen to burn, so when you remove the oxygen atmosphere, you remove the hazard.
Club Member
Joined: Apr 2013
Posts: 7,681
Likes: 8,413
From: Utah
Could you lower a small cup with water with a piece of dry ice into the tank. The co2 it gives off wouldmake it safe. And make sure the vent line is plugged.
Good luck, and have somebody filming when you strike the first arc
Good luck, and have somebody filming when you strike the first arc
Club Member
Joined: Mar 2009
Posts: 66,115
Likes: 51,405
From: Niles Canyon Ca.
That far away from the gas carry area your good, just wrap the tank in a couple wet towels, don't seal it completely let it breath and go for it just don't lay into it heavy to build up too much heat and you won't even bother the paint more than an inch away. I've welded more shovelhead fatbob tanks including split seams than I can remember with no issues.
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Club Member
Joined: Mar 2009
Posts: 66,115
Likes: 51,405
From: Niles Canyon Ca.
Skip filling it with water, more trouble than it's worth, you are welding a tab away from the tank itself. If you were going to burn on the tank proper then yes 90% full of water is how you do it, with a tab that far off just protect the paint well with the wet towels and and go for it.