It's always been an aggravation with my 1150GS that on a long main road cruise the low fuel light illuminates at around 160-180 miles and when you fill up you can only get 16 litres into it. The cause of course is that fuel is only taken from the right lobe of the tank and the two sides aren't connected. I wanted to solve this without resort to welding and the need to repaint the tank afterwards.
My prototype fix for this consists of 1 metre of fuel grade hose, 1 T-piece and a non return valve, all bought from Demon Tweeks.
The non return valve had a spring in it which took too much pressure to operate so I dismantled the unit, removed the spring and let the little ball valve work by gravity.
Next I cut two pieces of hose, one to feed into each lobe of the tank, connecting them to the T-piece but using it as a Y-piece. I then cut a shorter length to attach to the remaining arm on the T-piece at one end and to the “in” side of the non return valve. Finally another short piece of hose was connected to the “out” side of the valve.
Next I removed the filler cap and then the filler neck tube from the top of the tank. Using simple hand tools I cut a small recess into the bottom of the tube at the front sized to make the tube out from the NR valve a push fit, tight enough to hold the tube in place.
I then lowered the tubes into the front of each tank lobe and wedged the T(Y)-piece in front of the baffle plate that runs left of centre almost to the front of the tank. I then formed a small loop in the tube leading to the NR valve and located that by pushing the “out” side tube into the bottom of the filler neck tube. The fill tube and cap where then re-assembled. It was sunny when I did it so just leaving the cap “O” ring seal in the sun caused fuel to evaporate and it shrank back small enough to re-use.
How does it work? As you fill the tank the air is pushed out of the hose through the NR valve and with the well known drilled neck mod the fuel level can be brought right over the top of the hose located at the base of the neck. The petrol pump nozzle just fits past this hose. The hose is now full of fuel so as it is used and the level drops below the top of the tank “saddle” it starts to syphon from the left lobe to balance the levels. The idea seems to work very well running to 200+ miles before the light comes on. I am regularly running to 230+ miles and putting >23 litres of fuel into the tank. I pushed my luck the other day and ended up putting more than 24 litres into a standard 1150GS tank
I'll be making a better mark II version, probably with ductile copper pipe that will stay in place better in the tank.
My prototype fix for this consists of 1 metre of fuel grade hose, 1 T-piece and a non return valve, all bought from Demon Tweeks.
The non return valve had a spring in it which took too much pressure to operate so I dismantled the unit, removed the spring and let the little ball valve work by gravity.
Next I cut two pieces of hose, one to feed into each lobe of the tank, connecting them to the T-piece but using it as a Y-piece. I then cut a shorter length to attach to the remaining arm on the T-piece at one end and to the “in” side of the non return valve. Finally another short piece of hose was connected to the “out” side of the valve.
Next I removed the filler cap and then the filler neck tube from the top of the tank. Using simple hand tools I cut a small recess into the bottom of the tube at the front sized to make the tube out from the NR valve a push fit, tight enough to hold the tube in place.
I then lowered the tubes into the front of each tank lobe and wedged the T(Y)-piece in front of the baffle plate that runs left of centre almost to the front of the tank. I then formed a small loop in the tube leading to the NR valve and located that by pushing the “out” side tube into the bottom of the filler neck tube. The fill tube and cap where then re-assembled. It was sunny when I did it so just leaving the cap “O” ring seal in the sun caused fuel to evaporate and it shrank back small enough to re-use.
How does it work? As you fill the tank the air is pushed out of the hose through the NR valve and with the well known drilled neck mod the fuel level can be brought right over the top of the hose located at the base of the neck. The petrol pump nozzle just fits past this hose. The hose is now full of fuel so as it is used and the level drops below the top of the tank “saddle” it starts to syphon from the left lobe to balance the levels. The idea seems to work very well running to 200+ miles before the light comes on. I am regularly running to 230+ miles and putting >23 litres of fuel into the tank. I pushed my luck the other day and ended up putting more than 24 litres into a standard 1150GS tank
I'll be making a better mark II version, probably with ductile copper pipe that will stay in place better in the tank.
Thought you'd like to know the more modern, sleeker, faster GS12ADV has a transfer pump to do this job 
