You're right - big tanks are the way forward but:
1) they're more expensive.
2) usually bulkier and heavier than standard
3) often require extra taps/management of the quantity of fuel in each side.
4) not realistic to take off if you need to lift a heavy bike up on your own.
5) spend most of the trip only half full because you just don't usually need that much range!

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Find out details of my 2011 trip to Siberia on a lightweight dirtbike:
www.brighton2expeditions.co.uk

"My own personal view is that you would need to be nuts to consider such an option as a plan from the start....I would really have to be in a tight jam to consider..."

There aren't really aimed at people for Europe. Besides, if you need to use one you probably aren't going anywhere with nosey police or insurance agents...

This allows you to take on extra fuel when you really need it, at minimal cost, and without affecting the basic layout of your machine. This isn't strictly a plastic bag - it's a fuel bladder. Would F1 cars use 'plastic' bags to stop fuel leaks when tanks getting punctured? Yes they do.

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Find out details of my 2011 trip to Siberia on a lightweight dirtbike:
www.brighton2expeditions.co.uk

Oh, I've just had an email from the Bennetts representative in the Congo.
He says I can put my fuel in whatever I like

(ignore the last comment)

__________________
Find out details of my 2011 trip to Siberia on a lightweight dirtbike:
www.brighton2expeditions.co.uk

SMARTARSE....

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The electric monk always has faith.

I'll bet I can get Bennetts in the UK to agree to that too. There again, they think Morocco is in the EU, a leading link fork is some sort of electrical device and a Moto Guzzi is a Chinese grey import . (All true conversations I've had with their call centre. Devitt DA think a Ural has a built in intercom too????).

Big tanks are seriously overpriced. I added 8 litres for an extra 120 miles to my old F650 (carbed) for almost £400. That's £3 per mile over the bikes standard range. Norman Hyde want £800 for 2 gallons extra/90 miles/£8.80 per mile for the Bonneville. My auxilliary tank cost £70 for 10 litres and 100 miles on the Bonneville, or 70p per mile. A 10 litre jerry can would be down at 15p per mile with the hassle of having to stop and empty it into the bike.

The Acerbis tank broke it's fuel tap after a year (£30). The Aux tank is all welded, but I supose the in-line tap could go (£14). The jerry can is disposable, but they tend to last forever. The bladders replace the jerry cans very well, but take up a lot less space when empty.

To me they key is how often you use the range. I can easily go 200 miles without stopping, so a 120 mile tank is useless in Wales on a Sunday. I have come close to running out a 430 mile range F650 and a 420 mile range Bonneville two or three times. I can justify £150 worth of Aux/jerry can/bladders, but £400 of plastic, never again.

Andy

1) Yes but if you divide the price on 100kkms or more…
2) Not necessary heavier (my 43 liter tank is lighter then my 33 liter) and it carries the fuel lower then the original tank.
3) Is that a bad thing? You can double up with fuel filters, easier to fill your cooker etc.
4) If that’s a problem a bit of practice would help. I’m not athletic but I have no problems to lift up my bike with luggage and 43 liters of petrol.
5) I always fill my tank 100% but on average it’s half full :-)

1) 99% of bikes don't reach 100kkm. Divide by what? It's still more expensive
2) If you already had 33ltr you're in the wrong thread. I was thinking about bikes with half that!
3) I ride bikes not 747s. If I wanted to pump fuel around my bike I'd be in a different hobby
4) Lifting it up off the road in front of your house doesn't count
5) So you're always carrying twice as much fuel as you actually need?

Look, I'm only joking but I wanted to continue this thread to find out what sort of options are out there. I did the big bike/big tank thing and want to see if I could have more fun on lightweight thumper somewhere between here and siberia using something like this. I'll stop now..

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Find out details of my 2011 trip to Siberia on a lightweight dirtbike:
www.brighton2expeditions.co.uk

I have seen a DR350 with a similar tank (43L). The same statements are valid, except that the bike will probably not last 100kkm but he can move the tank to his next bike.