I feel like that would be a fuel filter issue...? Maybe not. I've never had that problem.
What kind of a set up are you running?
On the PA50's Keihin, The diameter of the fuel valve port can be enlarged by about 1mm and still be sealed by the stock float needle. The valve will seal a little more than 1mm higher so make sure to Adjust the float height to avoid pissing fuel everywhere. I think that the port is something like 2mm, so enlarging it to 3mm would deliver about 50% more fuel to the bowl.
A full tank of gas also helps with fuel pressure.