fuel filter

[Gnasher]

The filter is a possibility but it would have to be very dirty and would suggest other issues like contaminated fuel or corrosion in the fuel tank.  Easily checked this just bypass it, if all's well then the filter is indeed the issue also check the petcock tube gauze and inspect the inside of the tank for crap.  Along the same lines it's also possible the pump is failing that said from my experience pumps on Fazers either work or they don't but anything is possible.