Fuel Cell Mounting

Ron

Active Member
#1
I'm trying to mount a fuel cell to a dirt bike and looking for advice/other opinions. The bike I am using has a carburetor, FWIW.

My plan:
  1. Weld a small metal plate to the rear frame (see attached pictures)
  2. Attach a 2.5-3 gal plastic (plastic for weight savings) and use a T fitting to put it in before the fuel shutoff. Assuming the plastic tank will have mounting holes somewhere.
Thoughts? If nothing else, I have a backup plan to add a rotopax (which will be much simpler, but trying to save time here)




 

OX-34

Premier Member
IBR Finisher
#2
I mounted a 5 gallon (19 litre) aux on a bike with a tiny main tank of about 1.33 US gallons (5 litres). So I used the aux as the primary tank and had the bike tank as reserve. I put in an extra tap, easy on a carbed bike.




Welding a plate may not be needed, bolting a plate on should do the job. I would make it wide enough to use the outer bars of your stock rack and if possible project forward to take some support from the rack bolts or at least the angled bars. These are boat bimini fittings and come in multiple sizes and are very strong and can be used on round bars to hold metal brackets:



That is simply to shift some of the weight forward and away from the extreme rear of that bracket. Just having some form of fixed perimeter on the plate an inch or two high around the base of the tank will stop it moving forward/backward and side to side. A couple of cam-buckle straps or even better metal straps over the tank will hold it in place.

Although it is just a 5 gallon jerry can and strapped on, this set-up below had an alloy plate with upturned edges that fitted snugly around the base of the jerry can to stop it moving. The black tape was just there to hold the straps of an Airhawk cushion on the front that I used as a back rest. It was rock solid.

 
#3
Working out the plumping can be a brain teaser. On my CB550F I have a valve for both the main tank and the aux tank. The feed from the main and aux goes to a T fitting. What I have found is that if both valves are open on full tanks, the pressure in the line is sufficient to overpower the float valves. Solution is to run on Aux till you feel the bike running out of gas then turn on the main. No need to turn off the aux because it no longer will cause the overflow issue.

-Mark
 

Ron

Active Member
#4
Can you tie the main tanks reserve/main line together (via a "T"), and put the other fuel cell on reserve?

@OX-34 - on your aux tank.. was the fuel line able to pull enough pressure to suck air thru? I'm looking at marine tanks, and I suspect this may be the case. But I'm looking for confirmation
 

OX-34

Premier Member
IBR Finisher
#5
For clarity there is no 'main tank' and 'reserve tank' on carbureted bikes. It is just one tank with a higher-set outlet hose called 'main' and a lower-set outlet hose called 'reserve'.

Disconnect the 'main' hose at your petcock and blank it off by sticking a correctly sized bolt up the hose and clamp it with a pipe clamp. That way the bike's tank will drain fully via the 'reserve' hose. Attach the aux hose to 'main' on your petcock, and your bike's complete tank becomes the 'reserve' on the petcock. You could swap them, it doesn't matter, but just make sure you know which way the petcock has to point while thumping along in the middle of the night at 60 mph fiddling with your inner thigh. On a dirt bike I'm sure you will be trying to wring every last available drop of fuel.

The reason I put another inline tap in place was because I thought there was a chance that the head of pressure from that 19 litre JAZ tank may also fill up the main tank and potentially overflow right under my (iron) butt. I probably overthought it.;)

Ron the whole shebang is gravity fed, just like your stock bike. The fuel flowed just fine with a vent line drawing air into the top of the aux.
 
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EricV

Premier Member
IBR Finisher
#6
Great descriptions OX. Totally fits with KISS theory. And I heartily agree with mounting the aux cell as forward as possible to share some of the load on the seat or a plate to avoid the moment arm effect and potential over stressing of the rack. There have been a lot of cracked racks in the past from putting all the weight just on the rack. Those racks are usually only rated for ~11 lbs, but in real life we usually load them up a lot more! And fuel is heavy.

A simple aluminum plate spanning the rack and a portion of the seat, another piece of aluminum plate underneath the rack and bolt the two together will work fine if you place the bolts in such a manner that it prevents movement. (bolts against bars in the rack)
 

Ron

Active Member
#7
Sorry for the late reply (work is busier than usual)...

For clarity there is no 'main tank' and 'reserve tank' on carbureted bikes. It is just one tank with a higher-set outlet hose called 'main' and a lower-set outlet hose called 'reserve'.

Disconnect the 'main' hose at your petcock and blank it off by sticking a correctly sized bolt up the hose and clamp it with a pipe clamp. That way the bike's tank will drain fully via the 'reserve' hose. Attach the aux hose to 'main' on your petcock, and your bike's complete tank becomes the 'reserve' on the petcock. You could swap them, it doesn't matter, but just make sure you know which way the petcock has to point while thumping along in the middle of the night at 60 mph fiddling with your inner thigh. On a dirt bike I'm sure you will be trying to wring every last available drop of fuel.

The reason I put another inline tap in place was because I thought there was a chance that the head of pressure from that 19 litre JAZ tank may also fill up the main tank and potentially overflow right under my (iron) butt. I probably overthought it.;)

Ron the whole shebang is gravity fed, just like your stock bike. The fuel flowed just fine with a vent line drawing air into the top of the aux.
That makes sense - thank you for confirming my suspicions.

I'm primarily eyeing marine gas tanks (primarily due to weight and price). Any concerns with this approach?


Great descriptions OX. Totally fits with KISS theory. And I heartily agree with mounting the aux cell as forward as possible to share some of the load on the seat or a plate to avoid the moment arm effect and potential over stressing of the rack. There have been a lot of cracked racks in the past from putting all the weight just on the rack. Those racks are usually only rated for ~11 lbs, but in real life we usually load them up a lot more! And fuel is heavy.

A simple aluminum plate spanning the rack and a portion of the seat, another piece of aluminum plate underneath the rack and bolt the two together will work fine if you place the bolts in such a manner that it prevents movement. (bolts against bars in the rack)
I like the idea. Does the plate just rest on the rear seat than? My rack is already tied into the mounting bolts where the seat is..
 

EricV

Premier Member
IBR Finisher
#8
Marine tanks are usually pretty thin, so keep that in mind when looking at them. That's one reason they are not allowed in rallies. Depending on how big the seat is, extending the plate so it rests on the seat, but is still bolted to the rack area may take some of the weight off the rear rack and help reduce moment arm flexing. Ideally, when installed it would compress the seat a bit, or you would put some foam like a camp pad material in between the seat and the plate to get that compression, which would help minimize flex and absorb some vibration of the plate too.
 

OX-34

Premier Member
IBR Finisher
#9
Ron here's a pic of a Ninja 300 I rode on a couple of IBA rides. As Eric suggests, bringing the tank forward onto the seat is a great idea.

The Ninja had a rack off the back. I bought another pillion seat and made a mount for the front of the case - alloy bits you can see there.. You already have those good rack mounts on your bike. It shouldn't take too much effort to use them to hold the front of your aux cell.

In the dayride pic below I had a cloth strap holding the case down as an added security, but metal would be better.
Bylong valley copy 3.jpg
 

Ron

Active Member
#10
Woud something like this be acceptable for a gas tank than? They are about the only ones I can find that hold ~ 3 gal.. though I'm skeptical of an e-bay gas tank, because its ebay

Link
 

EricV

Premier Member
IBR Finisher
#12
Would something like this be acceptable for a gas tank than? They are about the only ones I can find that hold ~ 3 gal.. though I'm skeptical of an e-bay gas tank, because its ebay

Link
Yes, but if you're not going to do a rally, you can use anything you want. I'm just suggesting that you look hard at the marine tank and how you would mount it before you decide to use one. The dedicated fuel cells are usually thicker and tougher. Some of the marine tanks are roto-molded and pretty tough too. They used to be lighter weight in the old days. If you're thinking about the red polyethylene marine tanks, check one out in person and see what you think. I haven't looked at one in person in a long time, but remember them being about as thick as a regular gas can. You can strap it down, but in a crash it's not nearly as tough as a dedicated fuel cell.

There are lots of 3 gallon fuel cells out there. THIS ONE is about half the cost of the one you linked to. And has mounting tabs, with a nice, easy to use cap. You would want to swap to a tethered, non-vented cap, but the seller may have that option if you ask. Or find out the threads and you can likely buy a different cap from someone else that fits. Most companies use a standard thread in either corse or fine. A couple examples:
Corse thread Ratcheting & Fine thread tethered

Here is a plastic JAZ fuel cell for $140 - LINK Different shape.
 

Ron

Active Member
#13
Yes, but if you're not going to do a rally, you can use anything you want. I'm just suggesting that you look hard at the marine tank and how you would mount it before you decide to use one. The dedicated fuel cells are usually thicker and tougher. Some of the marine tanks are roto-molded and pretty tough too. They used to be lighter weight in the old days. If you're thinking about the red polyethylene marine tanks, check one out in person and see what you think. I haven't looked at one in person in a long time, but remember them being about as thick as a regular gas can. You can strap it down, but in a crash it's not nearly as tough as a dedicated fuel cell.

There are lots of 3 gallon fuel cells out there. THIS ONE is about half the cost of the one you linked to. And has mounting tabs, with a nice, easy to use cap. You would want to swap to a tethered, non-vented cap, but the seller may have that option if you ask. Or find out the threads and you can likely buy a different cap from someone else that fits. Most companies use a standard thread in either corse or fine. A couple examples:
Corse thread Ratcheting & Fine thread tethered

Here is a plastic JAZ fuel cell for $140 - LINK Different shape.
Eric,

I shoulda rephrased my post... the "ebay" one is the only one that I would find suitable for my application. I'm not doing standard pavement riding... If I do have a low speed accident (which is very likely), I want it to survive. I don't trust the plastic tank, or the welded tabs (I've heard horror stories of those breaking somewhere).
 

EricV

Premier Member
IBR Finisher
#14
Welds break when they flex. If you bolt/clamp a flat plate to the rear rack that spans the rear of the seat to keep the weight forward a bit, reducing the stress on the rear rack, and bolt the cell to the flat plate, the cell isn't going to flex against the plate. This stuff is a lot tougher than you may think, durability wise. I understand that a dusty butt ride is going to have greater vibration than the average street SS, but you should see the conditions most of the rally riders get into, often for many miles and using the same set up for years or even decades w/o failure. Where things break is where things flex. Tail draggers in Alaska have a rough go, for example.

Don't put lipstick on a pig. ;) Either the spun aluminum cell or The $102 square cell would be bolted to the flat plate. they have all the holes you need already threaded in the tank, both are simple to mount to a plate and just need a non-vented cap so you don't get fuel on the back of the bike. You can get a nice 3/16 to 1/4 plate of aluminum in any shape you want water jet cut for you someplace local to you w/o much fuss. Make a cardboard template and they can take it from there. Or just get a piece you like and trim it up, drill some holes, U-bolt it to the rack and bolt the cell to it.

The fueltankparts.com cell uses L pieces welded to the tank. The welds are not going to fail on that and as long as you aren't flexing the brackets, they sure won't break either. The clamps on the round cell will give you an equally low profile. Keep it simple. The fewer parts involved the fewer things to fail.

I've run various fuel cells since '04 and OX has run the same cell on many applications. (Plastic fuel cells are very tough.) Thee things are race applications and have quality standards to meet and testing standards for failure. They don't get approved if they are junk.

So, what is your goal for this set up? A particular ride/event or a cert ride of some kind? And what bike? Looks like an XR650 or similar.
 

Ron

Active Member
#15
The bike is an '05 CRF450X, see PM for further details. I low-key want to move it to other bikes afterwards (FJR1300/Harley Street Bob), but that's a separate discussion

I'm going to go forward with the spun tank, I honestly have a better gut feel about it than the other one. Mounting it on the rear part of the seat makes a lot of sense, I need to think on how it implement. What y'all say make sense, I just need to see pictures for me to put it together.
 

Ron

Active Member
#17
That does... thank you. I'm sure y'all mentioned this before, but I think I'll sling the plate under the rack and grab onto two of the rails. This will wedge the plate between the rack and the seat. From there, mount the tank to the rack.
 

OX-34

Premier Member
IBR Finisher
#18
My main concern with the barrel shaped tanks is how awkward and inefficient they are for packing in or around other luggage. More so when the aim is to use them on other bikes of no doubt different shapes and sizes.

I love a flat tank:






The initial set-up cost will be more expensive if you were to go down the flat-bed pathway, but they are just so easy to live with and an efficient use of space on all sorts of bikes.
 

Ron

Active Member
#19
Space on most of my bikes isn't a concern - I'd rather have something that's packaged "tighter". On all my bikes, I plan to put it where I have my current passenger seat (i.e., buy spare passenger seat.. add holes.. profit ;))

My final question - I understand that you don't want a vented gas tank to keep it from splashing on your back. But don't you need some sort of vent on a gas tank? Don't vented gas caps (like the ones here) prevent gas from leaking out/water from getting in?
 

EricV

Premier Member
IBR Finisher
#20
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.
 
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