Aux fuel setup

I finally got the 2.8gal "Tour Tank" mounted and plumbed in to my 2014 C650GT. I had the tank setup on my old Honda Silver Wing 600.
On that bike I ran the hose along the L side below the seat on the outside and then modified the fuel cap to add a swivel bulkhead fitting.
This mod was a little different as the fuel cap mod would not be possible, also I had to slightly modify the tank mounting plate to fit on the Givi top case mount bracket.
After finding the main tank vent, which is located in front of the sending unit and pump, I purchased a 1/4" brass tee, a .5 psi 1/4" check valve, a lighted rd panel mt switch, and a 1/4" npt 12v solenoid fuel valve.
After mounting the switch to the panel just below the handlebar lower cover and connecting it to the fuse block I had already mounted under the L front side cover, I rand the load wire under the plastic covering the tunnel and up to the area just under the seat along side the fuel pump and drilled a small 1/8" hole to bring it into the storage area.
I disconnected the 1/4" hose from the fuel vent and added a short piece of 1/4" fueline to the tee and then to the check valve and reconnected the vent tube to the check valve.
I then connected the 1/4" fuel line to the tee and drilled a 1" hole in the panel between the fuel pump area and the storage area.
I put a 1/4x1/4" npt hose barb on the output side of the solenoid valve, and a 5/16x1/4" npt hose barb on the input side of the valve.
I connected the wires on the valve to the one from the switch and to the seat latch mount for a ground, and after connecting the fuel lines to the valve I zip tied it to the frame rail on the L side storage area.
I drilled another hole on the back L side just inside the hand grips to run the 5/16" fuel line to connect to the tank.
Using the fuel line QD I had from my previous set up, I can disconnect from the aux tank without spilling a drop of fuel.
I plan on sealing up around the hole in the back with black RTV after I'm sure the set up works.
See pics attached
 

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  • fuel line and grd QD closeup.jpg
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  • fuel line and groound QD.jpg
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  • fuel line to under seat comp.jpg
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  • fuel solenoid valve.jpg
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  • fuse blk mt.jpg
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BMW n LA

New member
That’s awesome!! I purchased a 2014 C650GT last October and love this bike. My range varies from 180mi to 210mi per tank, depending on my wrist. Lol
I had hoped that BMW would offer their new scooters with improved mpg in the US.
I normally carry a 1gal tank for comfort especially when we occasionally extend our fuel stop.
Glad to know I’m not alone in ideas to extend range...
Cruise control would also be helpful..
 
I finally got the 2.8gal "Tour Tank" mounted and plumbed in to my 2014 C650GT. I had the tank setup on my old Honda Silver Wing 600.
On that bike I ran the hose along the L side below the seat on the outside and then modified the fuel cap to add a swivel bulkhead fitting.
This mod was a little different as the fuel cap mod would not be possible, also I had to slightly modify the tank mounting plate to fit on the Givi top case mount bracket.
After finding the main tank vent, which is located in front of the sending unit and pump, I purchased a 1/4" brass tee, a .5 psi 1/4" check valve, a lighted rd panel mt switch, and a 1/4" npt 12v solenoid fuel valve.
After mounting the switch to the panel just below the handlebar lower cover and connecting it to the fuse block I had already mounted under the L front side cover, I rand the load wire under the plastic covering the tunnel and up to the area just under the seat along side the fuel pump and drilled a small 1/8" hole to bring it into the storage area.
I disconnected the 1/4" hose from the fuel vent and added a short piece of 1/4" fueline to the tee and then to the check valve and reconnected the vent tube to the check valve.
I then connected the 1/4" fuel line to the tee and drilled a 1" hole in the panel between the fuel pump area and the storage area.
I put a 1/4x1/4" npt hose barb on the output side of the solenoid valve, and a 5/16x1/4" npt hose barb on the input side of the valve.
I connected the wires on the valve to the one from the switch and to the seat latch mount for a ground, and after connecting the fuel lines to the valve I zip tied it to the frame rail on the L side storage area.
I drilled another hole on the back L side just inside the hand grips to run the 5/16" fuel line to connect to the tank.
Using the fuel line QD I had from my previous set up, I can disconnect from the aux tank without spilling a drop of fuel.
I plan on sealing up around the hole in the back with black RTV after I'm sure the set up works.
See pics attached
Went for the 1st test ride of the fuel system and today and unfortunately it didn't work as expected.
I filled both tanks and went on a 165 mile ride and hit the solenoid valve switch at 1/2 tank, about 135 miles, rode all the way home but the aux tank never drained.
Once home I looked under the seat and immediately noticed the bullet connector on the wire from the switch to the valve had come loose.
After reconnecting it and turning on the switch again the aux tank began to drain into the main.
I taped both ends of the connector to the hose and tucked it behind the hose so it wouldn't happen again.
I also notice that while the bike was running and the tank was draining the fuel bars would not change until the bike was turned off and turned back on again.
I'll try another road test next week to be sure its all working fine.
 
Just an FYI for any one adding an aux fuel system to a C650GT, the fuel gauge, (bars) will not increase as the fuel is added to the main tank, in fact they will disappear at the usual rate even though the tank may be filling or even full. The change in bars will not be shown until the key is turned off and then back on.
Does anyone on the group know of a fix for this?
 
Just an FYI for any one adding an aux fuel system to a C650GT, the fuel gauge, (bars) will not increase as the fuel is added to the main tank, in fact they will disappear at the usual rate even though the tank may be filling or even full. The change in bars will not be shown until the key is turned off and then back on.
Does anyone on the group know of a fix for this?
Unless you can hack the ECU for C-series scoots, I don't think there's a work-around.

Based on my observations, the fuel system isn't an active measurement of the position of the fuel float, but instead the float position is polled during the pre-ignition cycle (ECU boot-up/diagnostics), a level is then set, and after that the ECU gives relative guesses regarding fuel levels until it's shut down again.

What's the grounds for all my fancy words up there? Simple. Try gassing up your scoot while the ignition is left on sometime. You'll see that the fuel gauge doesn't change until you power-cycle the bike, and it updates the tank status.

Basically, BMW is doing all the fuel computation based off an initial reading, and the feedback it gets whilst riding. They went drive-by-wire for this (rather than continuous analog readings), and they didn't anticipate someone like Freewheeling Frank improving the meager range of their scoots. :(

So while I'm ready to be astounded by someone Real Smart, I think this is a loop that BMW intended to remain closed. :p
 
Unless you can hack the ECU for C-series scoots, I don't think there's a work-around.

Based on my observations, the fuel system isn't an active measurement of the position of the fuel float, but instead the float position is polled during the pre-ignition cycle (ECU boot-up/diagnostics), a level is then set, and after that the ECU gives relative guesses regarding fuel levels until it's shut down again.

What's the grounds for all my fancy words up there? Simple. Try gassing up your scoot while the ignition is left on sometime. You'll see that the fuel gauge doesn't change until you power-cycle the bike, and it updates the tank status.

Basically, BMW is doing all the fuel computation based off an initial reading, and the feedback it gets whilst riding. They went drive-by-wire for this (rather than continuous analog readings), and they didn't anticipate someone like Freewheeling Frank improving the meager range of their scoots. :(

So while I'm ready to be astounded by someone Real Smart, I think this is a loop that BMW intended to remain closed. :p
Thanks for the info, MoE, I was afraid of that being the case as I asked my local dealer service rep about it and he said, "you need to figure your mileage, and ride accordingly".
I'm going to do a 1k in 24 soon this summer and check my mileage then as well with stops at about every 300-350 miles.
 
Funny, on my 2013 GT I can watch the bars go up as I am fueling.
So, took the bike out this am and gassed up, with the engine cut off (but the dashboard still active) and filled the gas tank up.

Fuel gauge didn't move until I switched the key position to OFF, then back on again, and immediately jumped from 2 bars (pre-fill-up level) to full.

I wonder how you got your fuel gauge to update while gassing up, @mjnorris -- did you leave the engine running?
 

mjnorris

Active member
So, took the bike out this am and gassed up, with the engine cut off (but the dashboard still active) and filled the gas tank up.

Fuel gauge didn't move until I switched the key position to OFF, then back on again, and immediately jumped from 2 bars (pre-fill-up level) to full.

I wonder how you got your fuel gauge to update while gassing up, @mjnorris -- did you leave the engine running?
Nope. I put the sidestand down which kills the engine and after opening the fuel cap cover I turn the key back on.
 
Just a note after test riding long distance to Sturgis last week, The solenoid valve worked good going up to the Rally, but on the way home in the heat, (95+ F) it would not open when energized.
Where it's mounted under the seat gets no ventilation so it got hot! Checked it the next day and it worked fine.
I'm still looking into getting a low pressure 12v pump, but it may allow fuel to pass when not energized, so I may still need a valve.
 
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