Fuel Cell Mounting

Ron

Active Member
#21
A big no on using a seat pan to mount a fuel cell. It's not designed to hold that kind of weight pulling UP when you crash, and they almost always let go and jettison, sometimes right into the back of the rider's head. Remove the seat, make a plate to BOLT down there, mount the cell to that.

Yes, all fuel cells need a vent or they won't flow. Some use a combo roll over valve/vent, others just use the existing hole in the tank at the highest point, (don't forget side stand tilt), and run a hose down to the back of the bike. Often angling off from the rear fender so it won't splash on the tire.

No, vented caps don't prevent gas from leaking out. Unless they are submerged, there isn't much chance of water getting in because the vent is not directly exposed. (edit - I see some of the ones you linked to have an exposed hole. If you look at them you will see it's nothing more than a hole thru the aluminum cap with a brass/bronze screen filter on the inside.)

The reason vented caps are not allowed, (and it's a bad idea for a moto), is it's very easy to fill the aux tank, ride off on a hot day and have the cold gas from the underground service station bulk tank start to warm up and expand. Now it's spraying or leaking out of that vented cap, and running all over the bike. A particular incident involving a Aprilla Caponord and a fire while riding to the Ancient Bristlecone Pine Forest comes to mind. It was a good day when the rider didn't burn down one of the oldest trees on the planet.
Duly noted on mounting of the fuel cell.

So, if I'm tracking this properly, I can buy the one I originally listed (here for reference) and apply one way vent to allow air in, but not out like so?
 

EricV

Premier Member
IBR Finisher
#22
Duly noted on mounting of the fuel cell.

So, if I'm tracking this properly, I can buy the one I originally listed (here for reference) and apply one way vent to allow air in, but not out like so?
Nothing wrong with that idea. But... the one way is not required. It sounds like a great idea, but sometimes causes issues too if liquid gets into it. (then it becomes a no-way valve) You just need a vent line that dumps beyond your rear tire safely. Should over flow occur. KISS. A simple vent line will both act as a vent in to allow flow from the Aux tank to the main, and as a vent out to allow over flow if/when that occurs due to expansion.
 

Ron

Active Member
#23
Nothing wrong with that idea. But... the one way is not required. It sounds like a great idea, but sometimes causes issues too if liquid gets into it. (then it becomes a no-way valve) You just need a vent line that dumps beyond your rear tire safely. Should over flow occur. KISS. A simple vent line will both act as a vent in to allow flow from the Aux tank to the main, and as a vent out to allow over flow if/when that occurs due to expansion.
Understood,

Thanks for the information/being patient with my questions!
 

EricV

Premier Member
IBR Finisher
#24
Understood,

Thanks for the information/being patient with my questions!
Questions are good! There are no bad questions, only ones not asked.

A common feature on vent lines is to put a small fuel filter on the end, or near the end, so dirt and other contaminates can't travel back into the aux fuel. Just a cheap plastic filter like THIS. That way you can visually check it too, and it's simple to replace, (or remove in an on the road, no time crisis). Carry a spare. Takes up hardly any space and you never know when you might need one.

I have run aux tanks with no vent line filter w/o noticeable issues for years. I always run an inline filter between the aux fuel and the main tank, (or carb in your case), and always carry a spare. This can be a life saver if you get bad gas at a station as you can quickly do a visual check of the filter and see contaminates. I am also a fan of using dry break fittings between the main and aux tanks, and running a exact duplicate pair on the vent line if I can run 5/16" ID hose for the vent line. This gives me a spare, just in case an o-ring dies on the fuel line set. That rarely happens, but can occur when you separate the dry break fittings.

I once had an electrical fault under the fuel tank during a multi-day rally. I pulled off at a remote gas station and got the seat off, lifted the tank, which requires separating the aux fuel line at the dry break, and repaired the electrical issue w/o drama. Then when I plugged the dry break fittings back in, (which had ~50k of use on them), one of the o-rings was leaking. Since I had a spare set, and carried small mini vise grips, it was a quick job to swap out the leaking fitting with a new one and get back on the road.

And a note on dry break fittings for fuel lines. Never, ever use plastic fuel line fittings. They will leak and break. BMW does this as OEM, much to the dispair of any BMW owner that had to deal with them. I'd use the Motion Pro ones on my lawn mower, but not on my bike. Marine dry break fittings or other quality fittings offer a much better life span and are much, much more tolerant of vibration and general moto use.
 

Ron

Active Member
#25
Questions are good! There are no bad questions, only ones not asked.

A common feature on vent lines is to put a small fuel filter on the end, or near the end, so dirt and other contaminates can't travel back into the aux fuel. Just a cheap plastic filter like THIS. That way you can visually check it too, and it's simple to replace, (or remove in an on the road, no time crisis). Carry a spare. Takes up hardly any space and you never know when you might need one.

I have run aux tanks with no vent line filter w/o noticeable issues for years. I always run an inline filter between the aux fuel and the main tank, (or carb in your case), and always carry a spare. This can be a life saver if you get bad gas at a station as you can quickly do a visual check of the filter and see contaminates. I am also a fan of using dry break fittings between the main and aux tanks, and running a exact duplicate pair on the vent line if I can run 5/16" ID hose for the vent line. This gives me a spare, just in case an o-ring dies on the fuel line set. That rarely happens, but can occur when you separate the dry break fittings.

I once had an electrical fault under the fuel tank during a multi-day rally. I pulled off at a remote gas station and got the seat off, lifted the tank, which requires separating the aux fuel line at the dry break, and repaired the electrical issue w/o drama. Then when I plugged the dry break fittings back in, (which had ~50k of use on them), one of the o-rings was leaking. Since I had a spare set, and carried small mini vise grips, it was a quick job to swap out the leaking fitting with a new one and get back on the road.

And a note on dry break fittings for fuel lines. Never, ever use plastic fuel line fittings. They will leak and break. BMW does this as OEM, much to the dispair of any BMW owner that had to deal with them. I'd use the Motion Pro ones on my lawn mower, but not on my bike. Marine dry break fittings or other quality fittings offer a much better life span and are much, much more tolerant of vibration and general moto use.
Have you ever had fuel flow problems? I've seen additional fuel filters cause flow issues (and sputtering). Unknown if it was because there was debris coming from the tank causing it.
 

EricV

Premier Member
IBR Finisher
#26
Have you ever had fuel flow problems? I've seen additional fuel filters cause flow issues (and sputtering). Unknown if it was because there was debris coming from the tank causing it.
I haven't personally had that problem. Gravity feed systems are what I've used. I have had crud in the fuel filter on the Aux tank line and changed it preemptively. I noticed at the end of a day during a rally that it was getting pretty dark. I had run turn a couple of aux tanks that day and just filled up with fresh gas, so wasn't going to flush out the aux tank, but did swap a new filter in and kept an eye on it the next day. (no further issues).

Flow issues are usually from line size or venting issues. I have had flow issues from vent lines with check valves that were stuck.

You should never be drawing fuel at a rate so slow that your engine is going to sputter. On gravity feed systems you open the aux tank well before you are empty on the main and let them equalize. If your entire aux tank is higher than your entire main tank, then you have to factor flow rate and figure out when to open the aux so it doesn't over flow the main, but you don't run the main down to critical low either.

Where I have seen what you describe is when people are using a vent line feed method. With the Aux tank being the only vent for the main and aux tank, and the main tank's vent line sucking fuel from the aux tank. There are several reason I don't care for that method, but to each their own.
 

Ron

Active Member
#27
IC. In the scenario I was mentioning, I believe it wasn't gravity fed (and it was between the gas tank and the carb, no aux tank involved) but rather vacuum, so that may be the difference. Once I get the bike back together I'll start ordering parts and maybe even post before & after pictures...!