Plumbing in rear tanks

[henryuk]

Dear all,

I have a tiny standard tank on my adventure bike - I can only get about 5 litres in it.

I am adding three extra 'tanks' (OK, they're just 5l jerry cans, peon that I am!). My question is this: what is the best way to 'plumb them in' - getting to the original tank is a PITA because you have to take the luggage partially off and lift the seat up.

Logic says that if I run a line from any of the higher up ones into a t-connector on the fuel line the fuel will overflow through the stock tank as it's lower down. Can you get either non-return valves that go inline in each fuel line, or a cheap switchable connector for fuel lines?

As my next adventure is a competitive rally I'd like to make switching tanks as easy as possible!

[Threewheelbonnie]

Vehicle wiring products and others sell an inline fuel tap http://www.vehicle-wiring-products.e...lpumps.php#atv (no association I'm just a customer), brass T off e-bay. My rear tank is in the previous pillion seat position so when full would be just higher than the main tank. The pipe run goes normal tap-T-carbs with the leg from the T going self sealing QD connector-inline tap- second tank. The inline tap is behind my knee, so easy to get to at low road speed, not so easy when shifting.

I fill both tanks with the taps off then turn on the auxilliary. At 90 miles or so I turn the main tap to on and hopefully the auxilliary off. If I can't reach the auxilliary tap without killing myself and get the switch over point wrong, the levels in the tanks will equalise. This is fine up to about 90 mph at which point the flow is interrupted enough by the siphon effect to get the odd feeling of running out. Not a big problem to me but who knows on another bike it could be a smaller window to change over in and might not just happen at stupid overtaking speeds. By about 150 miles I can just turn both taps on and go as fast as I like, it's just one big volume. Reserve is just like normal and comes up at about 250 miles. Somewhere about the 290 mile mark I'd be walking.

I played with a NRV to try and ease the flow and do away with the two tap set up. They are designed for fuel pump systems and open at about 1 bar against the balance springs and losses. You'd need the tank strapped to your helmet to get enough head to open the valve cleanly. With insufficient pressure the engine would need to pull vacuum to get it to open giving the same issues you are trying to cure due to valve hysterisis.

Don't forget the tank breathers, most MX shops sell little float valve breathers that let air in to stop vapour lock but stop fuel getting out if the tanks do have to level.

Piccies here https://sites.google.com/site/threew...d-improvements

I've had no bother on ferries (the tank is fitted, has a proper cap etc.) but you might with jerry cans. I remove it via the QD and fit the two person seat for MOT day, the pipework would confuse certain Quick Thick fitters as employed by VOSA. Take care if planning on going to Germany they might try legal stuff related to cans in the cities. I've had a petrol station attendant go "official" on me when I opened the second filler cap. He was fine once he saw it was bolted to the bike. Some sort of cover might be in order.

Andy

[backofbeyond]

Are you planning to use the jerry cans as fuel tanks (as opposed to just carrying spare fuel)? If so then presumably you'll be drilling them on the bottom for a fuel outlet spigot and working out some way of venting the cap. If you're doing that then I'd have thought an inline fuel tap per can would be all you'd need, together with a few T or Y pieces. Just switch them on or off as required.

Unless minutes really do count though I'd also have thought that each 5L "tank" of fuel would get you far enough that you'd need a break by the time it's used. Put some thought into quick release luggage fittings and just top the main tank up manually at each coffee / tea / toilet break.

[henryuk]

Thanks for the pointers!

To fill the main tank means lifting the box up to get the seat up - this might be trickey with 20+ kg in it - which would suggest plumbing in with some in-line taps would be better. I'm not confident I could plumb in a ower line into a plastic jerry without it leaking (as you couldn't get to the inside of it to add another rubber washer/nut).

Pros and cons for both approaches - I'll have to do some 'testing'.......

[Fantastic Mister Fox]

I'm interested in this as It looks like I'll be running one or 2 auxilluary tanks on my next adventure.

[henryuk]

Will you be running proper aux tanks? We were planning on having a few extra tanks but as the budget withers away we moved to three 5l plastic jerry cans per bike....

From the sounds of it TouringTeds solution of seperate fuel taps on each line onto a t-piece sounds ideal - solves the problem of different tank heights and therefore different amounts of hydraulic head and one tank siphoning into the other.

I reckon we'll just go with the decanting option. - Two people can refill the three bikes while the third one takes some petrol and brews up.

[Fantastic Mister Fox]

As much as we would like proper Aux tanks at £80 a pop they are quite a luxury.

I like the idea of 2 metal jerry cans with taps in the bottom, I'll attach them via a bracket to my luggage.

I think these will look better than the horrible looking plastic acerbis thing.

Will I have to plumb these in above the carb so gravity drives it into the tank?? or will the vacuum pull the fuel out if coming from the Aux tank/ Jerry can, My guess is if air tight the fuel will suck up but just checking.

[gixxer.rob]

Aren't jerry cans air tight ? If my memory is not deceiving me then you will have to put some sort of breather on them to allow the fuel to be drawn out.

I reckon you will have to give some thought to the position of the taps on the cans in relation to damage in the event of a crash. You wouldn't want to do a Hollywood style trail of fuel behind you

[backofbeyond]

Originally Posted by Fantastic Mister Fox

I like the idea of 2 metal jerry cans with taps in the bottom, I'll attach them via a bracket to my luggage.

Will I have to plumb these in above the carb so gravity drives it into the tank?? or will the vacuum pull the fuel out if coming from the Aux tank/ Jerry can, My guess is if air tight the fuel will suck up but just checking.

If you're mounting the cans on the rack at the rear of the bike you'll need some sort of pump to get fuel out of them and into the main tank. That means extra hardware, working out some means of venting the cap so that air can get in but fuel can't get out of the jerrycan and a labyrinth of piping taking fuel up to the main tank. You've then got to work out some way of getting it into the main tank - and if you want to transfer fuel on the move it'll have to be secure enough and the whole arrangement set up so that when the main tank is full it doesn't continue to fill and pour over your legs and the engine. It all seems more trouble than it's worth tbh.

If you want to work out some sort of syphon system you'll need to mount the cans above the main tank - probably on the handlebars! Good luck with that - and you'll still need to work out some way of venting the caps and plumbing the syphon. I'm aware of the Acerbis handlebar tank but can't find much info on whether it actually works or whether the bike just grinds to a halt with a vacuum in the main tank when the syphon fails to start.

Personally I'm all for simplicity and use gravity assisted manual transfer - unstrap the jerrycan and using manual dexterity transfer it to the front and tip it in. That system has not failed me yet and the Mk11 version, incorporating an off-line information transfer based upgrade, tidies up the major drawback - use a rolled up newspaper (or similar) to form a one shot funnel so you don't splash petrol over the tank graphics.

This is my current Jerrycan arrangement. Pic was taken in 2008 and no problems since.