Re: Petcock location on inframe fuel tank?
above the carb is best since it's gravity fed.
with the tank sloping down you won't get all the fuel out. there will be some vacuum with the engine running, but not enough once the fuel passes the petcock to drain the tank.
if you put it all the way back below and behind the carb, the weight of the fuel may be enough to push it to the carb, but as the fuel gets lower it might starve.
if the bike is running the vacuum might keep it flowing but starting it when the fuel is low could be a problem.
ideally you'd want to cut the tank open and block it off at the level point, but that's a lot of metal work.
if you cut down the motor mounts and get a shorty intake you may be able to lower the engine to squeeze a little more out of it.