Gas won't flow through fuel line

[gyraffoclops]

I'm running a 5/16 ID fuel line from the tank through a brass T fitting into two Mikuni Vm34's. I've double checked everything, the petcock flows freely, the gas line is free of debris but when its all on the bike together the fuel doesn't flow freely. there is a tiny bit of flow and air all in the line. It makes zero sense. Anybody had this problem and have suggestions? Thanks

 

[DaveO]

Blockage inside the tank? Just a thought, have you tried it with the filler cap off? (A blocked breather will mean no air can flow in, creating low pressure above the fuel).

(You'l have sorted it by now, obviously.)