Looking for some thoughts, advice, experiences in a similar vein...
The position of the factory fuel valve/petcock on my KLR650's gas tank leaves a fair amount of fuel below it in the lowest portions of the tank, never to be touched since it can't even be drained unless you were to remove the tank, open the cap and turn the tank upside down. The bike is, of course, a gravity feed carbed bike with no fuel pump. I have a new, larger plastic tank which I'm going to install soon. The unuseable fuel in this tank will be even greater if I re-use the factory petcock without any modifications.
The petcock is a simple fuel valve, a tube-like screen and a brass tube with the same kind of screen on the end of it creating the reserve and main fuel intake sources, respectively. My idea is a take on Skip Faulkner's fuel tank mod...I'm thinking of giving this a whirl:
Cut out "reserve" screen of petcock
Remove main brass intake tube (it's only press fit)
Cut it down to only an inch or so in length and bend it slightly if possible
Put this tube into the reserve intake position with the bend facing towards the front of the tank
Connect a ~12" long piece of Tygon fuel tubing to petcock
Insert petcock and tubing into tank
Fish out tubing from the cap opening, then attach a barbed in-tank style fuel filter to the end
Position fuel filter as low in the tank as possible with as horizontal angle as possible from filter to petcock
[This filter-to-tubing-to-tube intake would be the new "reserve", hence putting the tube in the reserve position on the petcock]
Install an in-line fuel filter post petcock since the new reserve fuel intake on the petcock would be without any screen
My main concern is that this in-tank "reserve" tubing won't be able to siphon fuel upwards at all...making this modification a total waste of time. If it is able to siphon fuel to the petcock, I wonder if it'll cause fuel starvation because the flow isn't sufficient.
And now I'm all ears