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Old 08-09-2008, 10:06 AM   #1
slide OP
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Joined: Jul 2003
Location: NM, USA
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BMW G-X Extending the Range or a GS-X

I'm crazy about my BMW G-X but the limited range (maybe 140 miles) limits where I feel comfortable taking it. In addition, my ideal G-X would be convertible from an around town speedster to an ultra lite GS - let's call it a GS-X.

First step was adding the SW Motech racks. The basic rack holds either a top box or various accessories as well as a large plate which is the base for strapping on soft bags and as much stuff as you want on top of it.



Shown here with the soft luggage converter. I can hang soft luggage from the sides or bungee / strap anything I wish to on to approx 16" x 10" or 40 cm x 25 cm plate. The large plate / rack removes without tools in a few seconds to return the bike to the stock look.

That was easy. Less easy was fuel. Advmember Hoots Magoon turned me on to the Acerbis auxiliary fuel tank meant to strap on a fork leg but capable of easily being plumbed into the factory tank. So I got one.

Now for the bracket which had to work both in 100% stock form and with the Motech rack(s). Here is the plate side view mounted to the bike. Note I used the rare material 'drillium' to lighten the plate. Even though it's aluminum, every gram counts, right?



Not obvious here but the offset is to make ultra sure the tank / plate clears the rear tire even if the tire were swollen with mud.

I had to offset the plate. If I didn't have the Motech rack system I could have mounted the tank much higher to clear the wheel. However, what I was faced with was either making a small offset and lowering the tank to clear the rack or making a large offset to clear the rack with the tank up high.

I chose to go lower feeling that keeping the mass down low was a good thing. I also did not want to widen the bike significantly as I'd have to do if I went with more offset. I braced the offset front and rear.



This is enough offset to clear the rear wheel easily. I gave it a lot of room so if the tank / plate move a bit whilst in motion, there is no possibility of it hitting the tire even at full deflection.

The nature of the BMW and the Motech mounting system required a bit of customization.



Another rare material - bendium - used for the top of the plate.

Finally the last matter - plumbing the Acerbis tank into the main tank. Hoots explained to me that the Acerbis siphons from itself into the main tank through the vent. As the main tank drains, the same amount of fuel gets pulled from the Acerbis replenishing the fuel consumed. In theory, a partial fill up will only require replenishing the Acerbis.



Acerbis supplies plenty of hose and the hose clamp to make a connection between its tank and the BMW internal one.

Well, that's it! My G-X is now a G-X convertible. I can pull the Acerbis tank with plate off with two bolts in maybe 3 minutes and the rack in 20 seconds. So in much less than 5 minutes I can have a stock G-X or a G-X with extended range or a G-X with a rack / luggage / top box or a GS-X complete with luggage, plate for strapping on anything I wish and an extended range.

I figure at adventure riding profile I get at 70 mpg. Thus I have a range now of 240 miles.



The GS-X in full dress w/o the side bags or top box. Note if you ride like Hoots, figure a range of maybe 210 miles only
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Old 08-09-2008, 10:33 AM   #2
GB
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Nice work!! I'm going to add this thread to the G650X Challenge index thread as an example of inexpensive DIY fuel range extender How many liters does that Acerbis tank hold?
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Old 08-09-2008, 10:40 AM   #3
Rolaro
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Can that weight be to much for the subframe ?

Reffering to Gazpipe frame cracks ??

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Old 08-09-2008, 10:44 AM   #4
slide OP
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The bike can take a passenger which would mean, say 170 lbs, so I don't think it's too much. The fuel / tank would be maybe 4 kg or 10 lbs total.
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Old 08-09-2008, 10:44 AM   #5
slide OP
A nation in despair
 
Joined: Jul 2003
Location: NM, USA
Oddometer: 21,122
Quote:
Originally Posted by Gadget Boy
Nice work!! I'm going to add this thread to the G650X Challenge index thread as an example of inexpensive DIY fuel range extender How many liters does that Acerbis tank hold?
Thx. GB.
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Old 08-09-2008, 03:25 PM   #6
Hoots Magoon
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Quote:
Originally Posted by slide
Note if you ride like Hoots, figure a range of maybe 210 miles only
SWEEEEEET.

I've had my Acerbis tank on for over a 1000 miles with no issues.

Lets see, 186.9 miles when the gas light came on. That would be 1.5 gallons used in the main tank plus 1.4 gallons from the Acerbis; 186.9 / 2.9 = 64.4 mpg. I would have 1 gallon left in the tank so 186.9 + 64.4 = A range 251.3 miles. That was on the Bayley-Hazen Military Road.

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Old 08-09-2008, 04:56 PM   #7
slide OP
A nation in despair
 
Joined: Jul 2003
Location: NM, USA
Oddometer: 21,122
I regularly get over 70 mpg mostly due to my elevation of 1.600 m or more. The area I wish to explore with the added range is at 1.800 m or more. Thus I figure a 250 mile range is easy and more likely.
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