Custom Motocycle Gas Tank

Fat Katz Trendsetterz

The scribe height was then set to 6-3/8 inches. Next, Brendon made sure the right-side tank fixture was set to the same height as the left. He told us this specific combination of scribe height and fixture height would yield a tank 12-1/2 inches wide at the front and tapering to about 2-1/4 inches wide at the rear.

Next, Brendon secured one of the tank halves to a fixture with some vice clamps so he could scribe his first trim line. Blue dykem was slathered on the tank to show the scribe line better.

The tank fixture can be raised or lowered to increase or decrease the amount of taper the tank will have. For this particular tank, the front of the fixture height was set to 4 inches tall, with the tail section of the fixture resting flat on the surface plate.

Then out came the plasma cutter, and Brendon cut out the basic shape of the tank half.

The tank half was set on the surface plate to see if it would rest flat. Any and all high spots were knocked down with a disc sander.

Once the tank was cut, Brendon knocked off all the slag from the edge and then used a set of trim shears to cut as close to his scribe line as possible.

Brendon set the scribe height to 1-1/8 inches for a 2-1/4-inch tunnel. He then squared up the edges of the tank half on the surface plate and measured in 5 inches to the tunnel at the front of the tank. A 2-1/4-inch circle stencil was used.

A tack weld was laid down every 1/2 inch or so. Brendon made sure to check the tank halves every so often to make sure they were still lining up.

The tunnel section for each side of the tank was then cut and fine-tuned with a disc grinder for a tight fit. Brendon then lined up the leading tunnel edges of the halves and began tack-welding the two tank halves together, starting at the front of the tanks.

Once the halves were tacked together, Brendon gave the top of the tank a thorough inspection to make sure he liked how everything lined up. Then he went back to the welding bench and made the final weld down the center of the tank.

Next, starting from the tail end, Brendon measured 19-1/2 inches up the center of the tank to locate where the gas cap would go. As we mentioned earlier, the Trendsetterz tanks come with the popular pop-up gas-cap feature that's found on many high-end bikes.

Once the location of the cap was marked, a 3/4-inch hole was drilled, and then a 2-1/4-inch punch and die was used to open the hole to the proper diameter.

To ensure a tight and flush fit for the gas-cap bung, the hole was then dimpled with a dimple and die.

The gas-cap bung was then welded in place.

The tail section of the tank then had to be measured and cut to fit the tunnel.

The tank and tunnel were then cut and/or drilled, and Brendon tack-welded the tunnel into position. Holes for the flush mounts were cut into the tank as well.

Next, the 1/4-inch stainless-steel hidden vent line and the bungs for the hidden crossover were installed in the tank.

These are the flush mounts Fat Katz welds into the bottom of its tanks. Before welding the mounts into the tank, Brendon cleaned up the mounting holes with a grinder for a tight fit.

He then used a guide tool to keep the mounts aligned when he weldeda them into position and then cleaned up the welds.

To make the front of the tunnel more rigid and help reduce the possibility of cracking, Fat Katz welds in this tunnel gusset for added reinforcement.

After everything was completely welded and sanded to a clean finish, Brendon installed the vent fitting (A) and hidden crossover kit, which consists of two banjo fittings and steel braided line (B).

Whether you're building a ground-up custom or are in the process of transforming your stock ride into a tricked-out head-turner, one of the most important parts that can often make or break the overall look is the gas tank. Sure, there are plenty of options to choose from, but that doesn't mean you should just jump at the first one you see. Obviously, the tank you choose should complement the style of bike you are building. For example, if you are going back to the '70s, maybe a Frisco-mounted sporty tank is what you're looking for. Maybe you are going for that long and low Pro-Street look? Then a sleek, stretched tank mounted low on the backbone is what you need. Maybe you need something totally different, something that hasn't been done yet. Whatever it is your project requires, Fat Katz, located in Grass Valley, CA, can handle your gas-tank needs.

Don Baumunk and his team of metal shapers have been building handmade custom gas tanks for the motorcycle industry since 1989 and have evolved their product line to include custom handmade fenders as well. Some of the latest developments from the Fat Katz facility over the past few years have been the option of steel tanks and its full custom tank program, in which you can order a custom tank made to fit any frame. The custom tanks start at about $2,450.

Fat Katz now also has its new line of Trendsetterz stamped custom tanks, which are made out of 16-gauge steel and range from $1,175 to $2,450. Fat Katz uses stamping for its most popular Trendsetterz tanks because stamping offers incredible consistency and finish. It also has the benefit of freeing up the craftsmen to take on more custom work and allows for a quicker turnaround. Each Trendstterz tank comes complete with all mounting hardware as well as hidden crossovers and vents to help hide unsightly components. For a real clean and custom look, the tanks also feature pop-up gas caps. Available in 16 different styles, the Trendsetterz tanks come in stock lengths for stock applications or stretched for custom frames with extended backbones. There are many options to choose from in the Trendsetterz line, from various tunnel widths and heights to different tail shapes, such as pointed or dovetail. This past fall we were cruising through the Grass Valley and decided to stop in to see how the crew at Fat Katz builds one of the company's stretched 940 Pro-Street Trendsetterz tanks.

We arrived at the shop bright and early, and Brendon Thompson was ready to build a tank. Brendon told us the reason Fat Katz build its tanks out of steel is that even though it's tougher to shape than aluminum, steel is more durable and sturdier, making for a solid tank that'll hold up through V-Twin vibration and abuse. Seen here is the left-side stamped tank half.

Before he could start, Brendon placed a left-side tank fixture (A) and scribe (B) on the surface plate (C). The surface plate is a precise, solid flat surface that is used to ensure that all measurements and scribe marks are even and consistent. The tank fixture and scribe are used to lay out the width and taper of the tank.

The tunnel section started out as a 16x25-inch sheet of 16-gauge steel. A bender was then set up to create the desired radius and depth of the tunnel. For this specific tank, the depth of the tunnel at the front of the tank was to be 5 inches. Brendon checked to make sure the tunnel fit snugly with as few gaps as possible. Some spots were too tight, so he had to grind them down. Next, he transferred the shape of the tank on to the tunnel with a pencil...

...and cut the tunnel to fit with trim shears. Before welding the tunnel into the tank, Brendon measured and marked where the tank mounts and petcock would go. For that custom uncluttered look, Fat Katz tanks feature hidden crossovers and a hidden vent line, which Brendon also measured and marked for installation.

Before any Fat Katz tank is shipped out, it is pressure-tested with 5 psi of air. Once the tank is inspected, the Fat Katz crew packs it into a box, along with the mounting tabs and rubber grommets, and ships it to your doorstep. Fat Katz recommends sealing the tank with tank sealer. Then apply a fresh coat of paint and mount the tank on the backbone of your ride, and you're ready to rock.