Article And Photos By: Daniel Donley
Originally Published In The November 2016 Issue Of Cycle Source Magazine
Got Sportster tank? It’s hard to beat the lines and traditional styling of a vintage sportster gas tank. They are small and compact in size and very easy to mount to your custom application. There are a few downfalls to the sportster tank, fuel capacity is typically only a couple gallons and without modification they are really only good for about half of that. Here at Pandemonium Custom Choppers I have come up with a few practical and cool modifications that I do to all of our sportster tanks. For this month’s tech I am going to show you these modifications and how I do them.
We are working with a reproduction sportster tank. You can also find used sportster tanks at the swap’s for reasonable prices. I first start by pouring a little bit of acetone inside of the gas tank and sloshing it around to remove any debris and or oil from the inside of the tank and then pouring it out. I use my air compressor to dry the acetone from the inside of the tank before welding or drilling on the tank.
One of the major issues with the stock sportster tank is the location of the petcock. It is in the middle of the tank, for us guys that are using them for a custom application you typically don’t mount these tanks level or parallel to the ground. They typically get mounted at an angle with the rear of the tank being much lower than the front. With the petcock located in the center you are not able to utilize all of the fuel in the tank. So this must go!
I use a 1 ½” hole saw bit to remove the stock petcock. Be sure to brace yourself and hang on to everything here because if the hole saw catches, I am telling you for FREE, it’s NOT GOOD!
Now that we have the stock petcock removed, we take the die grinder with a carbide burr bit to remove any sharp gnarly edges. You can also use a hand file here.
We also use a sanding disc to prep the surface for welding.
Another practical addition that I do to the sportster tank, is to install a tube fuel sight gauge. This will allow you to monitor the fuel level in your tank with a quick glance. Yes, they look cool but I also try to make sure when installing the bungs into the tank that they are positioned in such a way that the fuel sight gauge gives maximum viewing of fuel level. Anything after that is your “Reserve”. So with all of this in mind I laid out my fuel sight gauge location for drilling and used a sheet metal step drill bit to drill the holes.
Typically, the step drill bit will leave some gnarly burrs on the inside of the tank. I use a small round file to remove them.
I like to relocate the petcock to the most rear location of the tank, to get maximum fuel usage. I use a step drill bit for drilling here also. Along with a quick deburr with a small round file. Now the gas tank is full of metal shavings from drilling. I blow the inside of the gas tank out with compressed air to remove them. A quick shake of the tank will let you know if you got all of them.
Now, it’s time to start welding. Wait a minute we need to get this tank cleaned up. Use some acetone and a paper towel to clean all of your welding locations.
I cut a small round filler panel to fill in where the stock petcock location was. I also use a magnet to hold it in place then follow with multiple tack welds before welding it completely in. Sorry NO WELD PORN HERE!
It’s time to install the tube fuel sight gauge bungs. I typically position the bungs where they hang out the side of the tank about a ¼”, this will give you plenty to weld to and also let you move the bungs around so you can get a nice sight gauge position. I start with a couple small tack welds here, then loosely install the sight gauge fittings and tube. To see if I like the way the sight gauge flows with the contours of the tank, and carefully adjust the weld bungs accordingly. Now carefully remove the sight tube and fittings and add a few tack welds prior to final welding.
Everybody knows speed holes, fins, grooves and steps are cool. So with a quick trip to the lathe I whipped up a groovy petcock.
I typically put a small tack weld on the petcock bung.
Now with my petcock in hand I test fit the tank to the bike so I can get my petcock in proper location, prior to welding.
With the gas tank cooled from welding I use random plugs and fittings and gas cap to block off all of the holes for pressure testing. I like to pressure test my gas tanks at 3-4 PSI. I also use a mixture of soapy water to spray on all welded areas of the tank to check for bubbles. If you have bubbles then you have a leak. Re-weld if necessary. This one checked out great. I always like to metal finish all of my gas tanks to an 80grit finish with a D A sander. Take pride in your work and make it look the absolute best that you can.
Typically, the gas tank would go off to paint but for this application this tank will remain raw. I install my fuel sight gauge fittings with a little bit of Permatex ultra black on the threads and snug into position. Followed by the fuel sight gauge tube. Then I use SS safety wire for hose clamping. It adds a nice little detail.
The modifications to this tank are very straightforward and can be performed by anyone with fabrication skills. Not only does it look cool now, but all of these modifications serve a purpose and are very practical. For those of you who don’t have the fabrication skills or tools available to you. Modified sportster gas tanks are available on the Pandemonium Custom Choppers website. For the DIY’er Petcock relocation kits and fuel sight gauge kits are available there also. www. pandemoniumcustomchoppers.com