I thought I'd share my idea that's probably been done and isn't my idea but I thought of it and it works great.
So, I wanted extra fuel and I had a small outboard fuel can sitting on my shelf for 15 years. It was the right size and shape to strap on to the tunnel so I thought I'd use it. Problem being that since it's designed as a fuel cell it's not really great for pouring into the bike. It does have its own fuel pickup inside though, so I was trying to think of ways to pump air into the can or pump the fuel out. Then, I decided to try something a little out of the box. I took the breather line off my main bike tank and routed it to the red can output so it would suck fuel instead of air and the bikes breather valve thing was drilled into the cap of the tunnel can. It relies on the main bikes fuel cap actually sealing well enough that the main tank will draw from the supplemental and first, then when it's empty it draws air from that outboard tank to replace fuel in the mains.
Anyway it works great on my bike and has the advantage of not needing to stop and refuel, or monitor bike fuel levels.
There are several shapes and sizes but mine is similar to this one.
So, I wanted extra fuel and I had a small outboard fuel can sitting on my shelf for 15 years. It was the right size and shape to strap on to the tunnel so I thought I'd use it. Problem being that since it's designed as a fuel cell it's not really great for pouring into the bike. It does have its own fuel pickup inside though, so I was trying to think of ways to pump air into the can or pump the fuel out. Then, I decided to try something a little out of the box. I took the breather line off my main bike tank and routed it to the red can output so it would suck fuel instead of air and the bikes breather valve thing was drilled into the cap of the tunnel can. It relies on the main bikes fuel cap actually sealing well enough that the main tank will draw from the supplemental and first, then when it's empty it draws air from that outboard tank to replace fuel in the mains.
Anyway it works great on my bike and has the advantage of not needing to stop and refuel, or monitor bike fuel levels.
There are several shapes and sizes but mine is similar to this one.