Auxiliary Tank Usage

If you are new to an aux tank the following info will be helpful.

The system is entirely gravity feed. It is essentially a jerry can that is plumbed into the main tank. When the main tank gets low enough you open a valve on the aux tank to transfer the fuel from the aux to the main. 

Here is the process I have been using for years that works well for me. This process has been used on BMW and Triumph. 

  1. Wait until the low fuel light comes on.
  2. Open the aux tank valve.
  3. Monitor the low fuel light for it to go out. This gives you indication that you have fuel transfer to the main tank.
  4. Leave the aux tank valve open until you are ready for more fuel.
  5. Close the aux tank valve before refueling. This is important (see later).

Here are some caveats to be aware of:

  • If the aux tank valve is open when the main tank is full, you can overfill the main tank. If you have a bike WITHOUT emission controls, the overflow will spill to the ground and you'll likely lose all of your fuel.  If you have a bike WITH emission controls (most nowadays), the overflow will saturate the charcoal canister (part of the EVAP system) and cause the engine to run rough (rich) until the charcoal canister gets dried out. This can take a few minutes and will scare the snot out of you. I've only experienced this when the bike was parked. It may not happen if the bike is running but I've never experimented with this scenario.
  • The main tank vent is designed to let air IN not OUT. Filling the main tank this way is doing something the main tank wasn't designed to do; that is, to let air out of the vent. As such, fuel transfer can be slower than you expect.
  • The gas gauge will not respond quickly to the change in fuel level. It can sometimes be miles before the gauge will respond. That's why I monitor the low fuel light, it is much more responsive.
  • On rare occasions fuel transfer does not initiate. This seems to be related to the aux tank not venting. This is especially true if you have the overflow tank. Sometimes the siphon doesn't get started. This is nothing to worry about but can be a distraction. I decided once to just let it go and see what happened. My low fuel light stayed on and the distance to empty stayed at 0 for a long, long time. So long that I finally decided that what was happening was that when the main tank got low, below the fitting, a bit of air would go into the aux and allow some fuel to transfer. This was happening enough that I wasn't running out of gas but wasn't getting good fuel flow. Eventually, there was finally enough draw to make things work properly. The key thing to remember here is that you DO have 4 gallons of fuel, so don't worry!
  • If this bothers you (I know it does me) you can reach back and loosen the gas cap on the aux to start the flow. Don't forget to put it back on.
  • Finally, the BIG note. DON'T FORGET that you have drained your aux tank. There have been a few times (in a fatigued state) that I have waited until the low fuel light came on, reached back to open the aux valve and discovered that it was already OPEN. Yikes! You'd better be close to some gas and not on this road...

Image result for next fuel 150 miles sign


Print Email

Breaking News August 2019

Breaking News! UPDATE August, 2019

Farkles by Maple is back in business.

It's under new management with Jim Hatch. Jim is one of us and understands the demand for quality products. He has taken over my designs and has plans to improve and expand upon them. I'm pleased to have somebody take up where I have left off. I'll be providing web support, engineering support, and maybe even some moral support.

Many of the pages at were taken down and we are in the process of bringing relevant content back online.

Jim is now the primary contact.

Print Email

Breaking News January 2020

Breaking News! UPDATE January 2020


First, I'd like to apologize for the delays in getting Maple Farkles back rolling again. It's been a long road of education and juggling as well as waiting on equipment and tooling (more on that below). Over the past few months as hardware, parts and tooling came in from Mike & Walt along with the update, modification and acquisition of new tooling on my end; I've been replatforming Mike's designs onto a more robust CAD/CAM application (Autodesk's Fusion) so that I can drive the plasma cutting CNC table from the design files. This wasn't absolutely critical as we've created tanks using a shear cutter, but it will help with the precision needed for IBR certification and the repeatability of constructing tanks. Straight cuts are doable with a handheld cutter but slots, curves and holes definitely need computer control for quality production.

Based on the demand though it's clear a change in process is in order. I've spent the past few months fabricating tanks for local buyers - if something wasn't quite right in the translation to Fusion I could fix it easily. Based on those builds, I'm changing the way we're building and delivering aux tanks to the motorcycle market. Instead of building tanks one at a time based on individual orders, we're going to become a "stocking fabricator". This means we'll build and keep in stock several of each of the most in demand tanks so we can ship within a few days of receiving an order. Since a fair amount of the time required to make a tank is in tooling setup and prep, we'll be able to reduce this on a per tank basis and build each one in less total time. It also means customers will be able to tell when something is in stock and when it will ship. 

Of course some things will remain special order & built on-demand like custom powder coating colors and non-standard designs. But if you've got a BMW, FJR, Triumph or other common bike and you're good with a charcoal black powder coat you can have it when you order it.

Along with these changes we're also expanding staff - I've hired a welder to help out with the fabrication. One of us will cut and jig the setups while the other welds the tanks. Also, unlike Mike we're doing the entire fabrication process in house - everything from cutting steel to bending, bead blasting, welding and powder coat will be done in the shop. That way we're not trying to fit our schedule into another supplier's available time.

Together these changes should provide more delivery reliability and less waiting for aux tanks, racks and accessory shelves.

We're working on the production schedule now and will be updating this page with when you can expect tanks for your bike to be made. We're confirming the delivery of a new plasma table before finalizing the schedule but we're hoping to be able to throw some tanks in the back of the truck and see you at your favorite rally!


Print Email

Suzuki Water Buffalo

We've been doing some work with a client's water buffalo. For you younger folks, the water buffalo is a Suzuki GT750. The GT750 was a water-cooled three-cylinder two-stroke motorcycle made from 1971 to 1977, and was the first Japanese motorcycle with a liquid-cooled engine.

First off he had us make an aux tank. He opted for our Universal Auxiliary Tank. This was our first use of the very robust RAM Tough-Ball™ which has steel inside and out. He added the L-Track Tie Down Option.

Continue Reading

Print Email

  • 1
  • 2