For the Senior Butt Rally 2022 and the IBR 2023, I want to fit an Aux Tank to my Concours 1400, and aim for a fuel range of around 400+ miles ~650km.
I have some wider plans in terms of what tank, how to mount it etc, and all of these are contained by not wanting to undertake a ‘custom fabrication job’. Instead, I need to use simple, off the shelf parts, and need to keep all custom modifications on the bike down to an absolute minimum. This includes drilling the tank, I am fairly strongly trying to avoid having to do that.
When you consider the worst-case scenario, when you don’t have time to sufficiently spend with the bike, over a series of non-critical rides, bedding things in; you really can’t afford to be taking high risk chances when it comes to hitting the ground running in the USA, on a new bike, needing everything to work properly. – So I’ll make sure that all mods are reversible, actually easy to undo, and that they have a limited severity impact if they don’t end up working fully.
So, I’ve been aware of this pretty intricate fuel cap breather system on the C14; the vapour pressure is capable of being released through an intricate system inside of the gas cap, with filters, screens, sprung plungers etc, the cap itself has a little tube which seals inside of a rubber grommet inside of the cap’s well – this seals against a vent tube which returns back, through the tank, and exits towards the rear of the tank, there are two, one is a drain and the other is a vent. The drain simply drains any fluid from within the cap well, to the floor, the vent is well positioned into the tank, and if I could back-feed through this one; without disrupting any other operation of that vent, then I could use it to feed fuel in, from the Aux Tank, via a fuel pump.
I need a fuel pump because I’ll be fitting this as a ‘tail-dragger’ style of tank and naturally then, the height of the aux-tank is below that of the main tank. I need to use a tail-dragger because I will have Stella pillion on the back seat, and we also very much want to keep our Top Box because, we need it.
So… one thing at a time; all of this depends, ideally, on not-drilling-the-tank. If we need to do that, then I’m seriously re-thinking the approach. I might just carry a pumped Aux Tank and a loose tube end, and use it as a mobile petrol bowser. 🙂
Thankfully, it looks like we won’t need to do that, because during tonight’s testing, we had a whole heap of success – well worth building on… Our initial test, with all of the valving left in the cap was a fail, it leaked out through the key-hole, also into the cap’s well space, and then drained all over the floor – it was a complete fail. – I videod it, but it’s not worth sharing that complete disaster.
I returned to the garage to disassemble the cap, and to remove the complex innards to provide a much simple flow through the cap; even with these innards removed, we’re still limited to some pretty restrictive channels for the flow of fuel. One of the major ones is where it needs to pass through the final exit hole which is in the bottom, centre of the cap. This hole is only 2mm wide. There are other restrictive areas too but this is one which is so obviously restrictive and it’s also one which we’re able to do something further about, without ruining the cap’s normal function.
The cap assembly without itself is around US$130. So if it can be left intact, and returned to normal full operation once we’re done trying to run an Aux Tank, then all the better for that.
So, without further ado, here are my two testing videos, the first is just a general test, then I wanted to perform a timed test for 2L of fuel transfer into the tank. With the restrictions in the cap, it took 1 min to pump 2 litres. So in practice I would be able to empty a 5gal aux tank in about 10 mins on the road. In order to allow the pressures in the tank a change to return to normal I’d likely want to do that type of bulk transfer in 1 min periods, with a rest break between sending. I’m considering making an electronic controller for this, which would also incorporate an electronic fuel gauge for the aux tank. – Push and hold a button for 3 seconds to pump for 1 min, push and hold for 5 seconds to turn on, until turned off. All the while, showing how much fuel is likely left in the rear aux tank…
That’s another project; more on that later too.
Video 1: general test:
Video 2: timed test for 2L (spoiler alert, it took 1 minute):