Local guy with a K1100LT dropped by this morning to pick up an LED kit.

He has a custom aux fuel tank below the tail light and around the back wheel. Instead of having it go to the tank, he put a T connector into the return line from the fuel pressure regulator.  Although he has a fuel pump to move the fuel. he said he usually doesn't need it as the vacuum in the tank and the returning fuel refill the main tank for him.

So how does he refuel the auxiliary tank? I was looking at trying to only refuel in the original tank, to do that the auxiliary tank would have to be sealed and vented through the original tank, from back there it would seem hard to avoid airlocks during refuelling.

The aux tank has its own cap.

I forgot I had a my camera in my pocket or I would've taken a picture.

I'll email him and ask him to send me one.  It was a nice setup. I like the idea of keeping all of that weight lower down.

I worked out that by removing the battery etc its possible to get about 5 litres in the space. Relocate battery and coolant bottle and both are easy to do. But I keep coming up against the need for a separate filler cap which I would like to avoid. I suppose I shouldn't complain because that worked well for the Honda 50.

A bit of engineering, but why not mount the pump in the lower positioned aux tank and let the main tank gravity feed into it?
From FPR it could still go back to the main tank.

Just know when your low fuel light comes on you only have 12 litres left

Put the return line into the aux tank as the gravity feed could not possibly match the pump return and you would get fuel going everywhere.

Well spotted. My plan was to put the pump in the auxiliary tank, also the filter, with a screw on panel similar to what is done with most cars where you access under the rear seat through a panel in the car floor and then find a removable panel on top of the fuel tank to access the pump. I also think this would be a lot more accessible for service. I would plan to leave the warning lights as they are so they become 12 and 9 litre warnings. A 12 litre warning should be a comfortable amount for motorways with few service stations. It would make for a very usable 20-23 litres.

The tank itself is the easy part.

I have a feeling there is no problem using a different fuel pump as the fuel pressure is governed by the fuel pressure regulator.

The only concern I have is the that the gravity and pumped connection between the two tanks must be flexible. The easiest way is to use the same high pressure fuel hose. On most bikes though there is a fuel tap to turn off fuel flow when parked so that the contents of the petrol tank cannot drain. Any thoughts on a powered cut off wired via the ignition, ie fuel flow only occurs when the ignition is live? Its just a safety concern.

I like that idea.  I was with another rider with an aux tank last summer.  The rider left the valve on when in a store and that very thing happened.  Just a small puddle of gas formed under the bike before it was noticed but still....

Thanks Duck, I thought I was being a small bit pedantic but I do like to think through the potential side effects. A non return valve will work on the return to the original tank but the feed from the original tank to the new needs either a manual tap or a powered non cut off. I thought of a diaphragm but done really trust them. Manual tap doesn't really work well because its not very accessible.

On the K11LT I saw yesterday, he had a small petcock mounted the front hole for a Powerlet socket.

These coil plastic brackets are from a K1100 but they will fit on K100 coils.(I have them on my K100.)

Now you have given me an idea, the coil cover on the LT has a tab for a power socket.....just swap them and that's one item sorted out!

A 5 litre tank in here, plus Sidecar Paul's adjustment of the fuel cap would bring the fuel size to 30 litres.

I'm mystified at the - yes, I'll say it - obsession of some riders with huge amount of fuel storage capacity on their bikes.  How many riders face roads with fuel only every 300 miles?  
Not everyone plans to cross the breadth of Australia on an old K-bike, yet many seem to dream of just that.   

brickrider wrote:I'm mystified at the - yes, I'll say it - obsession of some riders with huge amount of fuel storage capacity on their bikes.  How many riders face roads with fuel only every 300 miles?  
Not everyone plans to cross the breadth of Australia on an old K-bike, yet many seem to dream of just that.   

At the beginning of this discussion my reason for wanting a greater range was a regular 170 mile work trip with 160 on motorway plus town trips at the end. Usually adds up to 200 miles before I leave for home which I would also like to do without having to find a gas station. The K is limited in range at 5,000rm and above, it would make my life much easier to be able to do the trip, plus my business at the other end, without having to exit the motorway or get petrol during the day. The return trips are also usually done late at night when most are closed. Gas stations have reduced considerably over the years and contrary to planning to cross Australia you will go many miles in rural areas at night in many countries without seeing a gas station never mind an open one. The aim was to have about 22-24 usable litres which on motorway speed is probably nearer to a comfortable range of about 200 miles. The west of Ireland, as it happens, has some of the most scenic routes but also has the fewest gas stations.

If you read other forums about travel in France you will also find plenty of warnings about motorways and the lack of fuel stops, some of them up to 50 miles apart with many closed on Sundays.

I happen to like to use the K for work but I also do up 25-30,000miles a year. I don't believe I ever mentioned about wanting to cross Australia on an old k bike, simply because I hate flying a as commercial passenger having done enough of it at work. The only way I will do a 24 hour flight to get there is in a box.
Duck had read my post and the reason and started a thread which I found very useful.

You can get 12volt fuel solenoids that will work with ignition on and close when off or the other way.  This subject has been getting a big thrashing on the Z1300 Kawasaki forum I go on as they have a bad habit of flooding the carbs and then filling the sump with the contents of the fuel tank because the Solex designed Mukini carbs don't have an overflow.  Many of the guys have been using Vacuum petcocks but they go directly into the base of the tank.

i was doing some poking around today and it seems as though using a solenoid with a gravity feed causes the feed from the aux to the main to be slow due to the small orifice size in most solenoid valves.

Here in the US, you can pretty much get gas 24x7 with a credit card, even at closed stations, so there's no real need unless you want to do the Iron Butt rally or similar.

I may experiment with it this spring since somebody gave me an aux tank for "free." (I did some work on his K1100LT in exchange for it.)

However, I'm not sure if I'd like that extra weight sloshing around up high and to the rear. My K1100LT handles much worse if I put too much weight in the top case. (Which I no longer do.)

Rick Many thanks for that one, its just what I wanted to find. It actually seems to make the task quite simple.

I wasn't trying to reinvent the wheel, just to be able to do my regular Cork Dublin trip on one tank of juice by adding extra range using fairly standard components. It does seem quite simple and also makes one task easier, a more accessible fuel pump and fuel filter.

In essence what is there now is to take the original flow connection from the Ks tank back to the auxiliary tank as a gravity supply in. The return fuel line still remains in its original position unaltered. That looks to be as simple as changing one fuel line by inserting the tank into the fuel supply line with a pumped supply from the new tank to the original fuel rail position. The return line remains unaltered.

On the electrics I plan to leave the 7 and 4 litre warnings unaltered. That will give me a 9 litre warning on the red. I can intersect the fuel pump electrics at the relay and route them to the new pump.

The only other thing is to sort the cut off solenoids and that seems quite straightforward, although I would like to take it from the fuel pump relay so they are both on the one circuit.

Making the tank is an easy part. I have checked that out and asked a fabricator who said if he is given a drawing or a full size mock up he will make one for very small money. The easiest way of working it out is of course a mock up made out of insulation as its possible to work out getting it in and out if necessary. The removable panel can be on top so that its not necessary to remove the tank to access the pump or filter.

Duck we do have some of those card pumps here too but not many. The problem we have is the absence of the petrol stations in the first place. In Europe most cars are diesel and have ranges of 500-700 or more miles on one tank of diesel and comfortably overcome this. Everything in the US seems to run on petrol/gas and have small ranges so you have plenty of gas stations. Some cars in the US struggle to do 150 miles on a tank of gas. But in parts of our county you can easily be 80 miles from an open petrol station at night.

There is also a pump system that the Kawasaki guys were talking of which is a vacuum powered low pressure pump with an auto shut off which could be used to pump fuel from ans aux tank to the main and you wouldn't need to move the pump etc. I shall try to find out more about it but its a very low volume forum so sometimes answers don't come quickly.
Just found this with a search which for once in my life worked.
"Now to get the pump go to your local John Deere dealer and get this part number (1-AM109212). This is the John Deere part number. This is a high volume pulse fuel pump. It is made by Mikuni. This has a fuel in, fuel out and vacuum in."
The guy said it worked on a Z1300 which gets at best 40mpg. From what I gather its a very low pressure so it doesn't override float levels that were gravity fed but will pump something like 16 litres/hour.
I am not quite sure how it could be incorporated but possibly via a switch to turn on vacuum when the fuel light comes on, then you would not have it flooding the full fuel tank.  Or even more simple a low pressure solid state pump that pumps when the low fuel light comes on.  Maybe just a manual switch to turn it on.

http://www.ebay.com.au/itm/Electric-Fuel-Pump-12-volt-Solid-State-4-to-6psi-130-LPH-Petrol-Universal-New-/130721428894?pt=AU_Car_Parts_Accessories&hash=item1e6f9ab59e

Duck,

I would struggle to put a fuel tank up high at the rear, weight is too much and yes, fuel slopping destabilises the bike. I take the top box off when I can and the difference is significant. I like the idea of it down low too because tank and pipes are well protected.

I could of course change the K to something different but it ticks every other box so I wont do that. I also happen to like the people I have met through the K.

Just another idea to add and hope I am not repeating anyone else's idea. 

With an aux tank, say of five litres mounted on the bike with location not important at this stage, I would be looking at the option of refuelling the main tank whilst riding. 

To do this, an internal pump with the fuel line tapped into the main tank return line with a T piece (and check valve) and an "Aux Fuel Pump" switch mounted in console for activation whilst riding.  An aux tank vent would be required to prevent a vacuum in aux tank during operation. 

With a know volume in the tank, a test of the system would be required to determine the exact time required to transfer fuel, to prevent cavitation or overheating of the aux fuel pump.  An internal or external pump could be used, with an internal reducing the volume of the tank but also allowing for cooling of the pump. 

Plumbing and wiring to be determined depending on the fit.  The tank would be single use and require an external cap for refuelling.  Possible the cap could also have the vent. 

Depending on the location, the Aux tank could be removable and used as required. 

Previous adaption of this idea that I have seen over the years include:
A bloke in Melbourne in late 1980s made a larger fuel tank for KRS which was wider with external dimension out to inside of fairing, (I may even have a photo somewhere)
Luftmesiter (?) made a pair of bulbous side cover which carried fuel for R series but this was a gravity feed system,
Recall a mate who made a fuel tank to fit inside of the duck tail on his Honda 750.

As Oz can be a large place at times, when travelling across the GAFA or up the guts, I have simply carried a spare fuel container on the back for use as required.

Just some ideas, T

RicK G wrote:There is also a pump system that the Kawasaki guys were talking of which is a vacuum powered low pressure pump with an auto shut off which could be used to pump fuel from ans aux tank to the main and you wouldn't need to move the pump etc. I shall try to find out more about it but its a very low volume forum so sometimes answers don't come quickly.

Rick,

I did think of this route but it seemed to involve a separate filler for the aux tank with a single supply up to the main tank, possibly by intercepting the fuel return. Making the tank under the seat fillable was getting complex as it involves finding space for a filler cap and also venting. It also still involves a pump and wiring for the aux tank and having to make sure the pipe into the main tank has a shut off.

An other solution when it's to far between the gas stations......start the cutting disc.   

Do you know how much that tank holds?

No idea, it was on ebay some years back.....US made.

Don't remember the name of the guy (he have passed away) which did
make a few of this fuel tanks...from what I have read on other forums.

I'll guess Duck knows more...

Something similar posted on this forum last year........Aussie made?
......I think that was written in the post.

Some guy from Tevas. I think his name  was Frank something.