Auxiliary Fuel Tank

[akbeemer]

Annie had an auxiliary fuel tank built for LBS sidecar rig. With the sidecar added, she can count on 30 MPG as a planning range. She can do better, but we always assume 150 Miles as her safe range on her 5 gallon OE tank. She has double that now (the aux tank is 5 gallons) and my GSA rig can be counted on to have a 240 mile range. Good numbers for our planned return to the Yukon and AK next spring.

We rode up to Kalispell last Saturday to have it installed. We saw 19 degrees near Lincoln. I took it off when we got home and had it powder coated. On the GS/A there is no need to put a hole in the OE fuel tank. The line from the aux tank attaches to where the breather hose on the tank and the fuel is constantly transferred by the vacuum created in the tank.

 

[omega man]

Someone did a very nice job on fabricating that tank. I will be interested in hearing how the draw/venting works out.
OM

 

[6322]

Nice! Fuel capacity and mileage are always on my mind as a hack driver. I carry a spare European can and funnel with about 2.5 gals. I remember being told years ago that it’s just as easy to fill the top half of your tank as it is the bottom half.

 

[BBrowning]

That is the trouble when you hack a GS. Fuel range. You are spot on with the 150 mile range, I can squeak out a bit more with my 2008 but usually dump one of my Roto Pac's in when I hit 150. Gives me a nice break as that is about the range of my butt too. LOL
Nice elegant solution so you both have roughly the same range.

 

[akbeemer]

After putting some miles on the auxiliary tank it is working as advertised. Annie started a ride yesterday with a 3/4 full motorcycle tank and she added 3.5 gallons to the auxiliary tank. After 15-20 miles her fuel gage read full. We rode 110 miles and her gage read full through out the ride. Her rig would typically use around 3 gallons on a ride of that distance.

The one change I would like to see in the auxiliary tank is a gage that shows how much fuel is in it. Not a critical issue, but would be helpful in determining remaining range.

 

[GTRider]

After putting some miles on the auxiliary tank it is working as advertised. Annie started a ride yesterday with a 3/4 full motorcycle tank and she added 3.5 gallons to the auxiliary tank. After 15-20 miles her fuel gage read full. We rode 110 miles and her gage read full through out the ride. Her rig would typically use around 3 gallons on a ride of that distance.

The one change I would like to see in the auxiliary tank is a gage that shows how much fuel is in it. Not a critical issue, but would be helpful in determining remaining range.

A question comes to mind. Most of the newer bikes have a vapor recovery system built in; the “charcoal canister” being one such example. In most of those applications there is a “biscuit” in the top portion of the fuel tank, designed to allow collection of vapors while excluding liquid fuel. But overfilling a tank can cause problems by immersing the biscuit and dumping liquid fuel into the vapor recovery system. Does the vacuum-based transfer system you are using maintain that headspace in the main tank, or is it possible for the main tank to have enough fuel drawn in via siphon to flood the vapor recovery system? I’d suspect that maintaining a good filler cap seal to be important vis a vis that headspace?

In the LDR community I’ve seen gravity feed, pump feed, and siphon feed used for aux fuel transfer. Both gravity feed and pump feed can bite the inattentive or forgetful user on the backside, so siphon feed is definitely appealing- but I’ve always wondered about that headspace and how one keeps the system sealed well enough to not create an issue.

Best,
DeVern

 

[pauls1150]

As a gauge, maybe a vertical tube "sight glass" like this?
Older bikes had a tube similar to this on their oil tanks.

 

[akbeemer]

A question comes to mind. Most of the newer bikes have a vapor recovery system built in; the “charcoal canister” being one such example. In most of those applications there is a “biscuit” in the top portion of the fuel tank, designed to allow collection of vapors while excluding liquid fuel. But overfilling a tank can cause problems by immersing the biscuit and dumping liquid fuel into the vapor recovery system. Does the vacuum-based transfer system you are using maintain that headspace in the main tank, or is it possible for the main tank to have enough fuel drawn in via siphon to flood the vapor recovery system? I’d suspect that maintaining a good filler cap seal to be important vis a vis that headspace?

In the LDR community I’ve seen gravity feed, pump feed, and siphon feed used for aux fuel transfer. Both gravity feed and pump feed can bite the inattentive or forgetful user on the backside, so siphon feed is definitely appealing- but I’ve always wondered about that headspace and how one keeps the system sealed well enough to not create an issue.

Best,
DeVern

As you surmised the seal of the tank is critical. When the tank was first installed the gasket was not properly sealing, once replaced, the fuel flowed as desired.

 

[akbeemer]

As a gauge, maybe a vertical tube "sight glass" like this?
Older bikes had a tube similar to this on their oil tanks.

Yes, that would work, but I’m not brave enough to drill the holes that would be needed to install it.

 

[skibum69]

What could possibly go wrong?

 

[lee]

I realize you need room for expansion but the filler tube shown in your pictures looks longer than needed.
What is the reason for that?

 

[akbeemer]

I realize you need room for expansion but the filler tube shown in your pictures looks longer than needed.
What is the reason for that?

More and more fuel pumps use vapor catchers that require the nozzle to be fully inserted so as to catch the fumes. This means the nozzle is so far into the tank that it will automatically shut off before the tank is anywhere near full. The tank is very shallow at the rear where the filling tube is located, making the longer tube necessary. Whether or not it needs to be as long as it is; that’s debatable.

 

[GTRider]

More and more fuel pumps use vapor catchers that require the nozzle to be fully inserted so as to catch the fumes. This means the nozzle is so far into the tank that it will automatically shut off before the tank is anywhere near full. The tank is very shallow at the rear where the filling tube is located, making the longer tube necessary. Whether or not it needs to be as long as it is; that’s debatable.

The solution to the “California Condom” at the gas pump:

Aluminum Gas Pump Nozzle Key

This nozzle key artfully retracts the corrugated... forepart of said alloy proboscis and allows you to gas your bike with a minimum of fuss and splatter.

www.aerostich.com

Best,
DeVern