Mounting a Deluxe/Standard tank on a Custom

Here is a detailed article on how to convert a Deluxe tank and seat for use on a Custom Model CX. Thanks, Larry.

After promising for a long time, this is my process of putting a Std./Deluxe tank on a custom cx500. In the past a lot of folks wanted a longer fuel range capacity than the Custom's small tank would provide. So putting a std. tank on a Custom model bike seemed like the logical thing to do. The problem was that the frame on the Custom model mounted the tank differently than the Standard/Deluxe model. So some modifications to mount the tank or needed. after doing this conversion a couple times I came up with what seems to be the simplest way to mount one, at least for me. Below is a step-by-step process of how I do my conversion using fairly common items, except for the welding equipment.

Okay so most of you know what a Custom model tank mounts like, with two bolts in the form of the tank and one in the back. The Standard tank has saddle's that slide over rubber lugs built into the frame. Resized to 44% (was 1023 x 685) - Click image to enlarge

One of the main problems with doing the conversion is that with the chrome headlight mounting brackets that slide over the fork tubes, tend to hit the tank at full turn left or right. The first thing that I do to correct this issue is to add a rubber spacer inside mounting the saddle of the standard tank. Since I've worked on cars most of my life I have several old shock absorber mounting rubbers in my junk drawers. Resized to 44% (was 1023 x 685) - Click image to enlarge

Cutting the rubber bushing in a little less than half, I use 3M double-sided emblem tape to secure it in place. This section of rubber keeps the tank far enough back so that the forks don't hit the tank at full turn. If you feel more secure in adding more space you can simply cut the rubber directly in half and trim it to fit the way you prefer. Resized to 44% (was 1023 x 685) - Click image to enlarge

I usually set mine up with at least a 1/8 inch space between the tank and the chrome headlight mount. Resized to 44% (was 1023 x 685) - Click image to enlarge

Because the custom model tank mounts with rubber grommets and bolted to the frame, the mounts on the frame are not wide enough to just slide the standard tank over the fittings. So an extension needs to be bolted to the side of it to come out far enough for the standard tank to mount securely. I found a tool at Home Depot that's used for floors and carpeted installation. HERE Taking it apart I use the two narrow ends as my tank mount extenders. To make it easier I use Allen headed bolts and drill the nylon so that the head of the bowl recesses into and under the surface of the spacer. The spacer itself usually needs to be made slightly thinner depending on the inner width of the standard tank. Most gas tanks have slightly different widths, so I can't give you an exact measurement of what to thin the spacers out to. Just drill and mount the spacers and see if the tank will go over it. If it doesn't, narrow each spacer evenly on both of them until you get the width you need to slide the tank over. Resized to 44% (was 1023 x 685) - Click image to enlarge

Now that the tank is mounted at the front the next step is to modify the rear Mount. The standard tank mount is farther back not only due to design, but the added space or in the front of the tank. When the tank sitting in place you'll notice a raised lip on the custom frame mount. Just inside that lip is where I cut the back of the tank off. Mark a straight line and either cut it with a hacksaw or cutoff wheel with an air grinder. Air grinder's easiest for me. Resized to 44% (was 1023 x 685) - Click image to enlarge

Resized to 44% (was 1023 x 685) - Click image to enlarge

With the tank sitting in a centered position I draw the center line and locate the position for the new mounting hole. In my opinion using the original mounting hole is too far forward. I forgot to take a picture of it, but in this position I drill a small hole through the back mount of the gas tank all the way through down to the frame. The whole ends up being about halfway between the original hole and the lip on the cross mount. Resized to 44% (was 1023 x 685) - Click image to enlarge

To make it easier to install and remove the tank in the future, I weld a nut on the backside of this hole. And to keep it all appearing stock I used a metric nut and bolt just like the original tank. Resized to 44% (was 1023 x 685) - Click image to enlarge

With the angle of the rear tank mount being slightly more than the amount on the frame, I find it nicer to cut out a section from the tank mount, and weld in a flat piece that matches the angle on the frame itself. You could make the rubber spacer that I'm going to make later in this post at an angle so it fits top and bottom. But in my opinion an angled wedge of rubber would tend to want to slide the tank forward, not that that would be bad. I'm just anal about details. Resized to 44% (was 1023 x 685) - Click image to enlarge

I simply cut a corner out of a piece of square tubing to the right width, trimmed it down to fit and well did it in. Followed by drilling the hole to match the one in the frame. Resized to 44% (was 1023 x 685) - Click image to enlarge

Resized to 44% (was 1023 x 685) - Click image to enlarge

To cushion the rear mount I simply used a section of the original tank rubber mount. Cutting the end off, trimming it to a rectangle and then grinding it down to about 3/8 of an inch thick. Of course drilling a hole through the center of it for the bolt. Resized to 44% (was 1023 x 685) - Click image to enlarge

Resized to 44% (was 1023 x 685) - Click image to enlarge

now as far as mounting the standard gas tank to a custom model bike, that's it. Like I said you could actually cut a wedged piece of rubber to mount the rear so you didn't have to do the welding and manufacturing, but in my opinion this is much cleaner and has proven to be easier in mounting the custom model seat. Which I will go into next.

Now that the tanks mounted it's time to move on to modifying the custom style seat if that's what you've chosen to use. As you can see the custom tank now hits the back of the tank and sits way too high. Resized to 44% (was 1023 x 685) - Click image to enlarge

To fix this problem I cut approximately 3/4 an inch or more off the front of the seat pan. Then I can start rolling the lip op and reshaping it to fit the rear of the tank. This takes a bit of doing with pie cuts in the metal as well as a bit of hammer and dolly work. Resized to 44% (was 1023 x 685) - Click image to enlarge

Resized to 44% (was 1023 x 685) - Click image to enlarge

Resized to 44% (was 1023 x 685) - Click image to enlarge

After getting the shape just right I weld up the cuts I made in the metal, bring everything down smooth and finish the shaping. Resized to 44% (was 1023 x 685) - Click image to enlarge

Now that the seat shaped, you'll find that the seat pan does not sit securely in position. It will go down too far since the stock rubber mount is no longer in use for it to sit on. But first of all I want to go through the steps to use the stock style lip mount. I made an aluminum plate that mounts to the two stock threaded studs on the bottom of the seat. As you can see at the front of the plate I tapered it so that it fits in between the frame rails and keeps the seat centered. I also had to cut a notch out in the center of the plate so it would slide over the mounting bolt for the tank. Some of these two steps takes a little trial and error to make sure you get it just right. Resized to 44% (was 1023 x 685) - Click image to enlarge

To get the seat to go down well enough I needed to hammer a recess on either side of the mount due to interference from the raised lip on the crossover mount for the tank. Resized to 44% (was 1023 x 685) - Click image to enlarge

The next issue was that the seat had nowhere to support the weight on the front when you set down on it. So to cure this, again, I found a set of hard rubber doorstops at Home Depot. HERE. I mounted them under the seat with large quarter-inch rivets and washers. But I did trim that outer lip off of it first. If I remember right I had to hammer the seat pan flat in the area where I mounted these rubber stoppers. Resized to 44% (was 1023 x 685) - Click image to enlarge

When everything was done, I simply added a little bit of foam cushion to the front of the original seat cushion and trimmed it to fit. Probably the easiest step so far. Resized to 44% (was 1023 x 685) - Click image to enlarge

Well, that's it. Here's the finished product. Plenty of gas, fit's well, and comes apart just like the OEM style design. Resized to 44% (was 1023 x 685) - Click image to enlarge