TOPIC:

OK Folks,
I've removed all the posts wherein we parsed/pissed our way through the numerous ways we might each describe the device used to shut off the flow of fuel from the fuel tank. If you wish to continue discussing the OP's topic please do so. If you want to further argue about the words best used, Please take it elsewhere.
Bill

Cautiously optimistic changing Pingel outlet direction and significant fuel hose length reduction will allow most of the fuel to drain from the tank. At least I can get some of the Reserve capacity fuel into the carbs now. Need to street test while carrying a couple gallons of extra fuel.

I know im going against the flow here[no pun intended]but is the length of fuel hose so crucial, surely once the fuel line is full as long as there is plenty of fuel in the tank it shouldn't make a difference to the fuel delivery, but then again my lack of technical knowledge is legendary.

paulb wrote: I know im going against the flow here[no pun intended]but is the length of fuel hose so crucial, surely once the fuel line is full as long as there is plenty of fuel in the tank it shouldn't make a difference to the fuel delivery, but then again my lack of technical knowledge is legendary.

The real issue is lack of head pressure when the tank is low on fuel. Just guessing, but the height differential is maybe 1 inch? Given that a water column 27.72 inches high generates 1 psi, then each inch of height generates .04 psig, not much.

And that's for water, which has a specific gravity of 1. Gasoline has a specific gravity of .739 which is why 1) gasoline floats on water, and 2) the resultant pressure drops to .027 psig.

So pretty much any flow obstruction (angled fittings, fuel filter, hose length and/or routing, tank not venting) will prevent the tank from fully draining.

Playing the numbers, roughly, when the tank is full, the height differential from fuel level at top to carb inlet is maybe, perhaps 7 inches or so? At 7 inches, .19 psig is generated. It's a wonder these tanks drain at all.

Sure hope my math is right..

Of note, these numbers based upon standard gravity.

I really don't think its the length of fuel hose, it is not 5 meter, it is 20-30 cm
from what I see the fuel line is curve up a bit and that can be the issue.
may be the aftermarket fuel valve (or however you want to call it), is sticking down too much and this cuase the curve

It's good to do the math so you fully appreciate what would happen when a fuel filter gets partially plugged.
Bottom line here for me is that this set up is not much different than a push lawn mower. The tank outlet is a few inches above the inlet to the carb and we seldom have fuel delivery issues with our lawn mowers right? The main difference here is that we are trying to feed 3 - 2 barrels carbs hungry for 24 times the amount of fuel of our lawnmower through the same size hose with the same head pressure. ( for the purists, assuming the lawnmower is 5 hp and the KZ1300 is 120 hp)
One thing that could plague a person without the knowledge or attention to detail could be if the fuel line rises above the bottom edge of the tank in vertical height. If you were near empty and went down a hill, the tank outlet could be above the fuel level and allow air in to the fuel line. That air bubble could effectively stop the fuel flow. Without enough pressure to push the fuel up and over the hump in the fuel line, fuel will not flow.
I'm sure all of us at some point in time got stuck for fuel and was forced to syphon fuel from a car gas tank with a piece of garden hose and we all know that if the hose in the tank isn't kept bellow the fuel level, you lose the syphoning effect and the fuel will not flow over the hump in the hose at the outlet of the tank. (God I can taste the gasoline right now !@#@!)
There are times when it's possible to get an air bubble in the fuel line and as long as the fuel line has a positive rise to the tank, the air bubble(s) will find it's way back in to the tank. If the fuel line has a solid column of fuel and no air bubbles, literally all the fuel in the tank will find it's way to the carb due to the syphoning effect but that's impossible because the bottom of the tank is relatively flat and at some point the tank outlet will eventually find itself above the fuel level and air ingress is inevitable.
That's my opinion for what it's worth.