If no one has one for sale, what style are you wanting? Flatbed, pillion seat area, tail dragger? Cheap and simple methods are available, but will require some effort. Figuring out how to mount a plate across your pillion seat and rear rack area isn't too hard. It's a good idea to keep the weight forward as much as possible to avoid subframe cracking.
Buy some foam craft boards at the Dollar Tree store and cut to the shape you like.
Decide if you're going to leave the pillion seat in place or remove it.
Figure out where you can bolt the plate up, what spacers you need to make it the angle you want or level.
How much size is available on the plate?
Spacers in all sizes can be found at ACE Hardware or any Farm Store like Wilco or Tractor Supply.
Now go look at fuel cells on ebay and other sources. Find one that will hold the fuel you want and fit the space you have. Buy it.
Place the fuel cell on your foam board that you've cut to the desired shape. Trim the foam board as required if the aux tank has a sump. Place your hose routing and make clearance cuts in the foam board as needed. Think about where your valve will be. Think about where your inline filter will be. Think about where your dry break fittings will be. (don't buy plastic drybreak fittings) Do by clear plastic fuel filters that don't come apart. Buy 3. One for the tank, one for the vent and one for a spare to keep on the bike. The vent one can be an emergency spare as well.
Once you're happy with the way the tank sits on the foam board, find a local shop that will cut that out in aluminum plate. I like 3/16" thickness, but sometimes you use what you can find. I've seen UHMW
cutting boardsused instead of aluminum.
A little thinner than I prefer, but with a flat fuel cell mounted to it, may be fine. Don't be afraid to think outside the box.
Buying a generic 5 gal fuel cell and having a modification to limit it to 4,8 gal can be done. Sometimes it's as simple as a sealed plastic container inserted into the fuel cell by removing the multi-bolt filler neck. One too large to pull out thru the neck, and large enough to offset the .2 gal, (25.6 oz). This handy and easily available device comes to mind -
LINK Drink contents, fill with spray foam or other non-soluble material and maybe a weight so it doesn't float inside the tank.
Are you going to
drill the tank for a bulkhead fitting, or use a siphon method?
This is a rough outline for a bolt together aux fuel system. If you have access to welders, there are options to keep the pieces to a minimum or have a more elegant mounting and securing method like the Tanji cells used.
