From: "DeVern Gerber" Date: Wed, 17 Feb 1999 23:41:44 -0700 Subject: Re: LDRider: fuel cell info for R1100RT I have a cell (good ol' Mr. Fusion) mounted on my R11RSL. The R11 series is fuel injected, so you will probably end up using a fuel pump to move fuel from the cell to the main tank. I say probably because experimentation on my R11 has shown that it is, indeed, possible to gravity feed the R11 system. Allow me to explain... Standard fuel cell setup on the fuel-injected BMWs is to run a pump feeding from the fuel cell into the RETURN fuel line from the fuel injection rail. Jan Cutler and Steve Losofsky pioneered this setup at Reno BMW (R.I.P.) after learning the hard way that K- bikes could sometimes do a masterful job of pressurizing their fuel tanks and pushing fuel out the vent line/cap on a fuel cell. Ask Jan sometime about that molten lump of aluminum in Austin, NV.... Anyway, when I first set up the cell on my R11 I followed suit and rigged a splice into the return line from the injector bodies. Problem was, there just isn't a good roomy place on the R11 to install such a splice without risking interference with the throttle cables or the cable drum on the right injector body. I had one that worked, but any mechanic who worked on the machine cussed that damned splice adapter anytime the throttle bodies had to be balanced or the tank removed. I myself grew tired of cussing at the thing and decided to start looking for a better connection point. First place I tried was on the fuel pump plate itself. While it would be easy enough to drill a hole in this plate and mount an aircraft bulkhead fitting, the tight fit of tank to frame would dictate at best an AN-4 fitting allowing only 1/4" line to be used. Also, this would add one more hose and one more connection under the tank to wrestle with when removing/installing the tank. The latter could be overcome by installing an in-line splice below the tank level, out in the clear, but I still didn't want to mess around trying to find just the right spot to mount the fitting. I looked at several other locations for the fuel transfer hookup and finally decided to bite the bullet and have it over; I drilled a hole in the bottom of the tank on the right- hand side and installed an AN-6 bulkhead ell fitting, making sure to use the appropriate aircraft sealing washers and nuts. I made sure that I used large-diameter washers on each side of the bulkhead, to better support the fitting. I then connected a 12-14 inch length of braided stainless fuel line, using an AN- fitting, to the bulkhead ell then on the other end installed an AN- union and braided line running up to the fuel pump on my cell. This has proven to be a very effective setup. Using AN-6 fittings and line I can pump 4.8 gals of fuel from cell to main tank in about 7.5 minutes. I use a push-button switch to control the pump, so I don't have to worry about leaving a switch on and pumping petrol overboard or burning up fuel pumps. The union in the line allows me to quickly and easily break the line so I can drain the tank dry for routine maintenance, a bonus I really appreciated the first time I removed the tank and didn't have droplets of fuel dripping onto my shoes or, worse yet, into my cold beer on the floor. When it comes time to sell the bike I will simply remove the bulkhead fitting from the tank and close the hole with an AN- plug fitting. As for the cell, it's a standard RCI cell mounted on the luggage rack using an aluminum plate bracket that I fabricated. I'll see if I can dig up a picture somewhere and post it, if you'd like. Lastly, I did some testing last fall where I eliminated the fuel pump and simply ran the tank on gravity feed. I can do this because A) I have the SHED system disconnected on my bike so the tank vents directly to atmosphere via both the vent line and the stock tank's overflow line, and B) my cell is mounted high enough to still maintain some head on the stock tank. However, while I will be carrying a short length of braided bypass line with me on future rallies I don't recommend the gravity feed. It doesn't allow me to shift all of the fuel forward and leave the cell empty like the pump does and, in light of Jan's experience, I still don't trust it completely. It is nice to know, however, that in case of a pump failure I can quickly rig a bypass. One last item... If you're going to mount a fuel cell please be willing to spend the time and money to do it right. Doing it right means a securely mounted cell, a fuel pump that is powered through a switched and fused hot line (I prefer to also use a relay on this so I can run light gauge switch wires), and fuel line fittings that are done right. IMHO, fuel line that will be exposed and susceptible to abrasion or impact in event of a mishap should be braided stainless covered line, connected via AN- fittings (aircraft fittings). I know, the stuff's expensive and hard to work with, but what good is having a foam- filled, securely mounted fuel cell if the fuel line pops off and begins spewing fuel at a mishap??? Do it right the first time..... Please feel free to write if I can help in any other way, DeVern