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Discussion Starter #1
I am mounting a 2.5 Gal aux fuell cell (Touring tank) which will sit on the luggage rack. My first impression tells me that the bottom of the aux tank will be higher than the bike's gas tank, and therefore I can arrange a gravity setup.

I have installed several Aux Fuel Cells on previous BMW's and always used a small pump, in one install to pump into the FI return line, in the other to pump directly into the tank via a tee in the "balance" line between the two sides of the tank.

Studying my manual I see that there is a drain hose and a roll-over valve hose, and neither is part of the pressurized FI system. Can I go into either of these hoses to transfer fuel by gravity from the aux cell?

Thanks, Stuart
 

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Stuart,

I think one of those two hoses goes to the drain hole in the upper part of the fuel cap, so it won't get the aux fuel where it needs to go. But the one with the one-way valve vents the internal tank so it may work. Keep in mind that the bottom of your aux tank will need to be higher than the top of the Triumph tank, assuming that's where the vent valve internal inlet is.

Good luck,
Bern
 

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Discussion Starter #3
I stopped over at my local dealer yesterday and spoke to Tom the mechanic. He said that the vent hose is not so simple, goes thru a pretty small passageway thru the tank top.

He suggested unbolting the fuel pump mounting plate and installing a fitting thru the plate. I'd probably tap it for 1/8NPT assuming the plate is thick enough. If not I'd weld the fitting into the plate. I guess I should replace the fuel filter while I'm in there anyway..... Hmmmm, thought this might be a simple job but I guess not. I'm still hoping that gravity might work here if the bottom of the aux tank is higher than the top of the bike's gas tank. If not a small pump from NAPA will ensure a quick transfer (3-4 min)

I could alway pull off the road and find a place where I could position the bike facing downhill for the fuel transfer. . . . . .

Stuart
 

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Id think the simplest fix would be a tee in the fuel return line, add a check valve at the tie in point, and a small switched transfer pump. Id check the fuel manifold pressure and make sure your transfer pump can supply pressure equal to or slightly greater than system pressure. Do you plan on stopping while refilling or doing it underway?
 

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Discussion Starter #5
I had such an arrangement on my BMW K1200LT. Had a tee in the return line, with the assumption that there was no significant pressure there, only enough to return to tank. The small pump from NAPA only put out 7 PSI so it was certainly no match for the 45 psi of the FI pump. It worked OK but the transfer of 3 gallons required nearly 15 minutes (always done underway).

On my BMW R1100S I found a static 1/4" ID line which connected to two sides of the tank, a "balance" line. I teed into this line and used the same type pump. I preferred this arrangement as I was not interfering with the FI system in any way. Transfer from my 2.5G tank required only about 4 minutes.

On the Sprint I would prefer NOT getting into the FI plumbing, and I think that a fitting thru the pump mounting plate would be the simplest AND may allow gravity transfer which I would like!

Thanks, Stuart
 

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I'm getting ready to start a similar project on my '03 ST - any progress? Pics?
How did it work out?

Did you tap the metal plate and use that as your source for the tank?
 

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i like the idea of the aux tank...Recently did a straight shot trip from Denver to Chicago and I must have had to refill about 7 times. Got annoying. Under normal riding...the stopping is welcomed though.
 

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interesting stuff... but how safe is that?

I mean, here in over-regulated, still without a government after 158 days after the elections, Belgium, I'm pretty sure that this is not allowed and in case of damages, the insurance company will use this to weasel out of payments.

what about over the big pond? do you need to tell insurance companies that you dragging a few litres extra fuel along??

just curious. Like the idea though, sounds ideal on a start of holiday doing the highway slab, which I try to get over and done with as quickly as possible and thus limiting the stops to as minimum as possible...

And I take the bruised nuts and sour bum the day after into the deal... :D don't like highways
 
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