Before our first Iron Butt ride last year I had a great idea. What would it take to add 5 more gallons to the BMW without setting a beer keg on the back seat. Having a brother who works sheet metal and such, I asked him to weld up two 2.5 tanks that would fit inside of my hard saddle bags. The right side tank has the filler neck and the main feed on the bottom left. Went to the auto parts store and picked up a small electric fuel pump. From the fuel pump it goes to the fuel by-pass line which goes into the tank. After all the hoses were in place time for a test. I put gas in the tanks and hit the switch located in the AUX position in the dash. It Works.
During the Iron Butt ride my dad riding a ST1300 had a 7 ish gallon tank and was very proud of not needing gas every 125 miles, like someone on a LITTLE 636
Now having a range of about 480 miles, I would show dad that at 375 I still had about 3 gallons or half a tank. It wasn't until the next stop did he find out about the hidden tanks in the saddle bags.