Fuel escaping at altitude
 

I'm having problems with fuel blowing back through the breather tube when I get above 8000 ft.
The bike is a G650 X Challenge with a Touratech 17 litre Safari tank (plumbed in as per Touratech instuctions, i.e. with 2 hoses coming from the OE tank to the TT tank) the fuel seems to be syphoning back from the OE tank into the TT tank and then blowing out of the TT tank breather, all over me and a nice hot engine doh
Any ideas for a fix please chaps as I'm in Bolivia and for the next 3 weeks I'm going to be above said altitude.

Cheers
Pete

It's out of equilibrium with the ambient pressure when it pisses fuel out of breather hose. I'm guessing something is wrong with the breather pipe's end that goes inside the tank (it's maybe loose and gets too deep inside the fuel - breather hose should be on top of the tank where no fuel gets) or is it the TT tank that is messing pressure up through the pump system you have for auxiliary tank? It shouldn't be coming out of breather if the tank is in the equilibrium with the surrounding environment's pressure (that's why there's the breather hose by design - there should be no vacuum nor overpressure). I'd look for the details that may create overpressure - i.e. a clogged breather hose on one of the tanks?

Not sure how this TT tank system works tho. Maybe one of the tanks has no breather so the fuel can be pushed (with intentional overpressure) from one to another tank(?) This can be your source of problems.