Yamaha FJR Auxiliary Fuel Cell Version II - CNC Mount

"The only time you have too much fuel is when you're on fire."


Having already used an auxiliary tank on my Concours, I just had to have one on the FJR.

But then the Givi rack broke and I lost an auxiliary tank in the process. At the time that I found the Givi rack, it was a blessing to find a way to mount the tank.  I never liked the industrial look though. 

My first thought was to clean up the broken ends and just mount the tank to the stub of the Givi rack. It would have stuck out the back a bit less which was one thing I never liked with the original. It also gave me the opportunity to slightly redesign the tank. It was a bit too tall for my tastes. And, there was room for a little more in the fore & aft dimension.

Notice anything missing off this Givi rack ?

What I really wanted was to be able to retain the factory rack / grab handles. I didn't want to drill any new holes in the bike or the rack. I wanted the mount and tank to look like Yamaha shipped it that way.

A while after making this plate, I found that buried under the tail plastic were two more threaded sockets which the OEM accessory top box bolts to. By using these two sockets to bolt down to, plus the center bolt just to the rear, plus the rack itself, I'm reasonably confident that this tank will stay put. The bonus is that I can retain the stock rack and passenger grab handles.

A while back, I was looking to make a part for the bike but knew that I couldn't do it by hand. So, I built a small CNC milling system for home. I recently bought a new X and Y axis which really extended the cutting envelope. That's what made making these plates possible.

Here's Version 2 of the mount. ( No, it won't end up on the top of the tank when installed, that's just where I took the picture.) It's a bit thick but that makes the threaded holes a bit meatier. Unnecessary weight, yes, but not so much that it will have much affect on anything.

This is where the top plate will sit. The two large holes on the forward end of the plate match up with the threaded sockets in the frame. It means drilling two more holes in the tail plastic. I'll put a nut on each bolt under the plate and tighten it up against the underside of the plate. That way, the threaded sockets will also support the weight of the tank.

With this new mount, the tank should sit just a little bit lower and forward. That should also help with the aesthetics.

You can see that the center bolt through the rack is just about in the center of the holes in the aluminum plate. That's where I want the weight to be. With the whole thing tilted slightly forward, and my recollection of high school physics and vectors, the weight should be fairly nicely distributed on all the the support points. The plastic rack should not be supporting much of the weight, certainly no more than it was designed to.

The FJR Aux Tank - Version II holds a bit over 11 Liters or about 2.9 U.S. gallons. That's an increase in the stock tank's pre-reserve fuel capacity of 55%.

I much prefer the looks of this tank over Version I. This one is 4.50 inches tall whereas Version I  was 6 inches - a 25% reduction in height. I managed to get the same capacity by stretching the front to back measurement by 1 inch.

Now for a bit of grinding, sanding, and painting...

After a little time with a random orbital sander to slightly clean up the welds and scuff up the surface for better paint adhesion, and a couple coats of pickup truck bed finish.

 Not bolted down yet, but the final installation should look just like this.

The view from the gas station that you just passed without stopping.

This is the petcock that I bought. It's a Pingel #1210-AH. It's far better than the one I used on the Connie tank. It has no reserve and the lever movement is oh so smooth compared to the Connie aux tank valve. You can just feel the quality of this little gem. This is not the place to try saving a few dollars. I had to order it directly from Pingel as nobody stocks this one. Yes, I checked. I paid about $60 for it. Expensive, but I like the quality and the screen is far better than the one on my Connie aux tank. And it's rebuildable.

Pingel is quite specific about instructions on sealing the threads. According to the instructions, Teflon tape should be used on the threads. I just learned that there is the hardware store Teflon tape for plumbing and air fittings and then there is the "other" kind for gasoline environments. Buy the YELLOW tape in the YELLOW package. It says right on it that it can be used in "pipe assemblies handling gasoline..."  "You must apply at least 3 revolutions. DO NOT use Teflon liquid or pipe dope, use only Teflon tape."

Filler cap

It's a non-vented cap from Mark Williams Enterprises

The weld in bung also from Mark Williams. I think that Sampson Sport Touring also sells these. Pingel too.

There's a really good article on installing a fitting to your stock tank so you can transfer the fuel in from the aux tank. You can buy the fittings from Sampson Sport Touring. I bought one of these and really liked it.

I mounted it on that quarter sized dimple in the bottom of the tank but the o-ring is about the same size as the tank dimple so be very careful, otherwise you may end up with the o-ring staggered on the edge of the dimple a bit and it may not seal properly. So far, so good.

The above link shows the use of two O-rings. I went to the McMaster-Carr website, a very good supplier for the bulkhead fittings. They show using just one O-ring. Drawing at right. They say "Through-wall fittings, which are also known as bulkhead fittings, allow you to make safe, quick inlets and outlets in plastic and metal tanks, walls, and panels for faucets, pipes, and spigots. To install, start by depressurizing and draining your tank. Cut a hole in your tank, slide the body of the fitting through the hole from the inside of the tank (make sure the gasket is against the inside tank wall), and tighten the nut on the outside of the tank."


I'll bet you wondered like I did, about how you were going to get your tank off without spilling any gas. These fuel line quick disconnects also come from Sampson. A quick Google and these were the only metal ones I found. Not sure if they're any better or not than the usual plastic models.

You may want an inline fuel filter or two as well. Carry a spare. If it clogs up, you may be hooped until you find another one. Or get one of those fancy dancy aluminum body models that you can clean all the schmegma out of. Remember to be sure that you orient the filter to the proper flow direction. There's usually an arrow on the casing. I just cleaned out the filter on my Concours. After seeing the crud in there, damned rights I'll put one on the FJR.. It was the one on the right. Now, in hindsight, that's the one to go with as they are easy to clean if you don't have a new one on hand.

Although the Pingel petcock has a very nice, fine screen in place, I added a filter just in case. I also left a fair bit of extra hose in place until either I need the space or find out the optimum amount needed to  move things around, change tail light bulbs, etc. Then I'll shorten it a bit.

You get another angle of the grommet here too.

After mounting the Version 1 cell, I headed from Vancouver to Halifax, Nova Scotia. I did a Trans Canada Gold ride on the way back and the cell worked just as intended. It's easy to lean back and flip the petcock open while on the move. Range was about 600 Km's / 360 Miles. I never had the opportunity to push it that far but I knew my math was right. I did have 3 legs of about 500 Km's though.

 Updated January 30, 2009