Article By: Tyler Malinky
When it comes to mounting a custom gas tank on your bike, there are many ways to skin a cat. With quite a few tanks coming with welded on but undrilled tabs, one of the easiest ways is to weld a couple of threaded bungs into the back bone of your frame. Tophat-style bungs are ideal as they will sit up a bit off the frame and stay put while you tack and weld them in place. Welding a solid bung into your frame is much safer than simply drilling a hole and through-bolting your tank in place; an unsavory practice you likely have come across if you drag home project bikes from time to time.
The first place to start would be to mark the center of your gas tank tabs, centerpunch and drill them out for the hardware you plan on using (5/16” or 3/8” diameter, either is fine, this is often based on how much room you have on your tabs). Set your tank on the backbone and mark and centerpunch where you want your front tank mount to be. Drill a small pilot hole, carefully keeping it on your centerpunch so your hole isn’t off center.
One of the easiest ways to drill a large hole is with a step bit (a.k.a. unibit) which allows you to drill through several sizes of holes without changing the bit, though you can also use large drill bits as pictured. In the case of our tophat bungs, you would drill the hole out to 3/4” so the 1” diameter flange sits on top of the tubing.
Tack the first bung in place in a couple of spots and weld all the way around. You can now bolt your tank in place into the first finished bung, and carefully mark the center of the rear mounting hole so you can drill the frame for the final mount. Once you drill the hole and set the bung in place, check the spacing and fitment multiple times before your final welds to ensure everything will bolt up properly.
That is it. A leather or rubber washer between your frame and tank tabs to protect the paint, and you are good to go!