Frequently Asked Questions

Here are a series of questions and answers which should help your understanding of our products and services.

Auxiliary Fuel Cell General

A lot of folks think it's so we can go further. That's one benefit but not the most important. The main reason is to be able to manage your stops. How many times have you stopped for fuel when you didn't need fuel but you didn't know if you could make it to the next available location? Lot's I'm sure. The aux fuel gives you the ability to drive across the desert in the middle of the night and not worry about running out of gas.
Tank placement is mostly a function of whether the bike is used for 2-up riding and whether one wants to retain a top box.

There are 3 options for mounting a tank:

  1. On the tail rack (to retain the pillion seat for 2-up riding)
  2. Forward of the tail rack and over the pillion seat (to retain a top box)
  3. Over the tail rack and over the pillion seat. (as you may have seen with the FJR)

It is always better to move the load on a motorcycle as far forward as possible. That being said, there may be reasons for keeping it on the tail rack. We have one client with hip problems and with a forward mounted cell she wouldn't be able to throw her leg over the seat. The first cell I made a cell for my K1200LT was option 1. The second was option 3. I had been using the pillion seat area for storage of my road food and drinks. I missed that with option 3 so I ended up going back to option 1. You can see pix of those two examples here Option 1 / Option 3

Another factor in a forward mounted cell is that it can be used as a backrest. Since backrests can run 100s of $ this is certainly a consideration.

Unless there is a technical reason that requires a fuel pump, gravity is preferred. With a fuel pump you have more points of failure than with a gravity fed system.
There are several factors that will impact fuel transfer rates: hose size, number of fittings and/or valves, gravity or pump system, height and distance between aux tank and main tank, to name the big ones.

Our experience with gravity fed systems on most bikes is a transfer rate of 8 to 10 gallons per hour using 1/4" hose, 1 shut off valve, 4 hose barb fittings, and one valved quick disconnect assembly. This means that a 5 gallon aux tank will transfer to the main tank in 45 minutes or so.

See the question, What fuel transfer rate is fast enough?
There are two answers to this question.

The first answer is based on your subjective preference. If you want to open the valve and see your gas gauge immediately begin to rise then you need to have a VERY high transfer rate. One measured in gallons per minute instead of gallons per hour. Some folks will build those systems but we recommend considering the technical answer.

The technical answer is that you want to have a system that refills your main tank at least as fast as you are burning it up. Our gravity fed systems are delivering 8 to 10 gallons per hour. Since we all use MPG calculations this needs to be translated.

Here are some mpg/mph averages that translated to GPH
100mph/25mpg=4gph (this is a rate consistant with most high performance motorcycles)

Check out this article where we detail how we do it. Auxiliary Tank Usage

Plumbing a Fuel Cell

For a gravity fed system you will need a shut off valve, a bulkhead fitting (to tap into the main tank), and the fittings and fuel line to connect these together.

For a pumped system you will need all of the above, plus a fuel transfer pump and electrical connections.

With either system you have some options. such as a quick connect fitting or fuel filter. While the quick connect is not required, it does facilitate maintenance, whether you are removing the aux tank or the main tank.

This is a personal preference. We can install one for you if you request it. If not requested we don't put one in since we don't see any potential of fuel contamination with our tanks.

The bulkhead fittings we provide require a 3/4" hole drilled into the main tank and access to the inside of the tank to tighten the retaining nut. In many cases, this is the most complex (and scary) part of the installation. We have provided detailed installation instructions for the models we done. See Documentation.

We're not fans of AN fittings, they are expensive and hard to find. If you're not flying an airplane or driving a race vehicle, we just don't see the advantage. Bear in mind AN fittings have two advantages. They support metalic shielded lines and large sizes. Those advantages are important to aircraft where a fuel leak could be catastrophic, and for vehicles that are burning tremendous amounts of fuel--like those dragsters that go thru 5 gallons in less than 10 seconds.

Our default configurations use 1/4" hose and barbs, and 1/4" NPT pipe fittings. You see a lot of discussion about hose size but in our experience 1/4" gets the job done, is easier to route, and fittings are marginally less expensive.

That being said, it is important to note that we operate under two simple rules: 1) the customer is always right, 2) if the customer is wrong see rule number one.

We specialize in custom builds and we will build anything you spec and are willing to pay for so don't let our personal opinion impact your decision to use our services.

Well high is subjective. You can find lower prices, especially if you buy quantities. First off, we're not in the plumbing hardware business but offer these fittings as a convenience to our client's. Secondly, our pricing is competitive with the local hardware stores when you include your travel expense and time.

We've done quite a bit of homework on this subject and have read many MDS's. Here's our takeaway, Standard Nitrile is also known as Buna-N. It is rated as having excellent resistance to petroleum-based oils and fuels, water and alcohols. Nitrile also has good resistance to acids and bases, except those with a strong oxidizing effect.

So unless you have some specific requirements (i.e. material type, durometer, color, tensile strength, elongation, or standardized composites such as published by organizations like the FDA, NSF, Military, AMS, ASTM, DIN, ISO) then Buna-N is perfectly acceptable for our uses. A good, and very readable reference is O-Ring Application Guide from Fluid Seals.

Tank Construction and Fabrication

We do not use foam. All of our tanks are internally baffled using 5052 aluminum in accordance with IBA specifications.

"A minimum of 80% of the dry capacity of the auxiliary tank must be filled with anti-slosh foam, or the tank must be equipped with one or more longitudinally-placed baffles that are at least 80% of the height of the tank and that divide the tank into two or more chambers of approximately equal volume."

The purpose of the baffle is to prevent a shift in weight which would impact the handling or stability of the motorcycle.

From a manufacturer's standpoint we have an additional concern, how any shift in weight will impact the mounting points of the tank. For example, we just fabricated a cell that not very deep and was twice as long as it was wide. The longitudinal 50/50 rule didn't satisfy our concern for a radical front to rear or vice versa load shift. We figured a sudden acceleration/deceleration was much more likely than a quick side-to-side transition. Plus the front/rear forces on the mountings would be much greater than the side-to-side.

|We balanced the requirements by placing two diagonal baffles.


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