Just wondering what you guys think. The L bracket that attaches the gas tank to the frame on the S40 broke on this last trip. Even if I could weld, I do not think I would attempt to weld on a gas tank. I am therefore thinking of reattaching the L bracket to the tank with JB Weld. Is this futile or is it worth a try?

The bracket would be much stronger brazed.
Sometimes paying for something is better.
A bodyman at the local bent car fixit shop could do that either brazing or not welding in a few minutes.
You should be in and out for twenty bucks and a twelve pack.

You might have to check a few places, if you see a bike in the parking lot, best start.
Dealership shops, meh, probably not.
Independent shops, best bet.
Announcing yourself and needs at the office
Not best approach
Mozy in a back door, strike up a conversation with a bodyman, ask about guys who do work at home, blah,blah,  you get the idea..

Just my opinion and my experience, as best as I can remember it.

JB Weld, steel putty, and such things set up ROCK hard.  There is no flex. They will crack.  The first time mine broke, I used steel putty. My welder cussed up a storm as he had to grind it off then I had to have it bead blasted, so he could weld to metal.  He bent and welded a plate over the crack in the bend.  The next time, the bracket cracked at the end of his plate.  The next time (or the time after?), a spot weld that holds the bracket to the tank broke and gas was leaking.  He wouldn't touch that.  He would have had to cut the bracket off and redo the entire thing. I filled around the bracket with JB weld.  That was when I started looking for a new tank.

Once that bracket breaks, there is no fix that will last forever.  But I went YEARS on those fixes.   Each one lasted a good while.
AND, you have to remember, I ride off road.. too much...  Much more abuse than usual.

I have also went through two rear fenders.  Learned my lesson from those and I packed the third one with steel putty in the void between the fender and the license plate bracket before I put it into service.  No problems.. yet.

Just an odd thought...
I wonder if a super magnet or two attached to the bracket would be strong enough to hold the tank in place?
https://www.globalindustrial.com/p/neodymium-super-magnet-assembly-na011200n-...

Cool Sero. That is thinking outside the box!

Thanks MM. I have not taken the tank off yet. The bike was washed in put in the garage. I am riding the Honda for now. Since I have not taken the tank off I am not sure what you are referring to when you say what the other side looks like. Here is the picture I took of it.

It appears your bracket is broken all the way through.  Welding or brazing it would provide a repair that will likely be fine for a very long time.  If you were here I would Mig weld it for you in a couple of minutes.....easy fix and it would not even mar the visible paint on top of the tank (you would need to remove the paint for 1/4 inch either side of the crack.  Brazing requires a lot of torch heat and definitely would get a lot of heat into the tank.....it would be my second choice for a repair.  JB Weld would not hold unless you used a repair plate to span across the crack and provide a lot of surface area for the epoxy to grab onto.....and the parts need to have the paint removed and roughed up where you will be applying the JBWeld.

I have a blue tank that is nearly perfect if you decide to replace your tank...I think this is the same color as your bike.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1615654773

Wet rags can keep heat away from places