Had to remove the floorboards today to adjust the bands and this gave me the opportunity to do something I have long wanted to do.
I hooked a clear vinyl tube to the gas tank and checked the actual head or pressure at the carb inlet:
With 6.25 inches of gas in the tank I measured 7.5" head at the carb inlet. When the tank is nearing empty there is only 1.25" of head at the inlet. Not much!
If my math is right that works out to 0.033 psi pressure at the carb inlet when the tank is nearing empty. Good reason to use a large line and no sharp bends or restrictions !
Cheers
schuh