Early on in the process, I decided that the large square ugly gas tank would be swapped off with a custom tank on the Honda CX500 Cafe Racer build. The photo above shows the original tank on the right, and the modified later model CX500C tank on the left. I cut out the recessed fuel cap, and installed a weld in fuel cap bung made by drag specialties that takes Harley Davidson 84-E96 vented right hand thread compatible fuel caps. I wanted a nice clean looking tank and this seemed like the way to go. The new tank is about half the volume, but I’m not concerned this is not going to be a touring motorcycle and 2.5 gallons of fuel is more then sufficient.
Somewhat surprising but two significant modifications had to be made to the frame to make the Honda CX500C tank fit and mount up on my CX500 model bike. I initially thought that it would be an easy bolt on swap when I picked up the smaller much more attractive looking CX500 custom fuel tank. I first moved the rear mount such that the tank would fit over the stock mounting points used on the original tank. I bored out the metal washers so they would fit over the studs. I used this method to locate the rear mount, which I cut off the frame and ended up moving about 2″ forward. This put the tank in the right spot such that the indents for the coils on the underside of the tank were in the correct location. I turned some custom threaded bosses on the lathe for new front mounts. Then I cut off the original studs and tack welded the new threaded bosses onto the frame located centered over the original studs location. When the frame is stripped for painting I’ll finish weld the mounting bosses in place.
After I moved the mounts and the tank was mounted to the frame it was time to do a little custom work on the top of the tank. I wanted a cleaner look then the ugly stock flap over locking fuel cap. First I cut out some sheet steel to fit the opening roughly. Then I used the planishing hammer to form the compound curves. It is harder to make a compound curved piece of metal then most people think. A lot of careful hammering, planishing, and bending got the fit just right so the curves matched up perfectly.
I left a bit of the recess lip on the inside of the tank. This should provide additional strength to the top of the tank and help with any oil canning and distortion from welding. This type of welding requires very large amounts of patience. The goal is to keep the metal cool the entire time so you don’t get oil canning or warping of your metal due to excessive heat. Lots of little spot welds with cooling time in between keeps things from getting too hot.
The finished weld looks good. Still needs some prep work prior to painting but nothing more then a skim coat of filler will be needed for a flawlessly perfect finish on the tank.
The tank is ready for final stripping, metal prep, priming and painting. This is some of the last fabrication and customization of the original Honda CX500 frame. Soon I’ll pull the motor and remaining parts to strip and paint the frame/rear swing arm and start the reassembly of the bike for spring riding. I’ve been sandblasting restoring and painting the small parts all winter in preparation of the reassembly of the bike.
6 thoughts on “CX500C fuel tank swap on the Cafe Racer”
Great job, you have some serious fabrication skills. I am looking for a replacement tank for my CX500 D. If you still have the one you swapped out would you be interested in selling it?
Sorry Scott, I sold the original tank on Ebay some time ago. At the time there were plenty of them on Ebay going for reasonable money. Good luck with your bike!
I figured you had sold it but couldn’t hurt to ask. I am checking ebay frequently, there are plenty of custom tanks but the deluxe/standard tanks are rarer. I will get one eventually.