Cut wires from a rigged up tail light and now the head light don't work, the fuel pump don't prime and the bike won't start. Bike ran fine the day before.

Take the cables loose from the battery. Clean the cables. Might need a wire brush. Reconnect.

the pump itself isnt any good. replace it and ride.

Turn the bike off with the kill switch. Turn the key and listen for the pump to prime.
If it doesn't.
Check all fuses.
Check your fuel pump relay fuse - try taking it out and putting it back in.
Check you main fuse next to the battery (30A).
If you replaced any fairings or did any modifications to the bike, make sure you didn't mess up the BAS\Roll over sensor as the bike may think its on its side and will not pump fuel.
Check all wires in the wiring harness make sure there is no corrosion and the fuel pump relay is getting power.

Check the fuses, especially the fuel pump fuse. Then, check to see if voltage is getting to the fuel pump wires. (1 wire should get battery voltage) If fuse and voltage to pump is good, replace fuel pump.
Fuel pump replacement requires a special tool.

BAD STARTER SWITCH

check for a short in the wireing harness trace signal wires from relay to lights see where the break is look for any spots that may have rubbed through

i had same problem turned out to be electrical issue check all your wiring connections under the seat and under your fuel tank and if there all fine try checking that your fuel pump motor is running mine wasnt because of damp on my wiring connectors. when you turn on the ignition the bike should click a few times and your fuel pump should come on look under your tank looks like this with 2 tubes running from your fuel tank http://cgi.ebay.co.uk/yamaha-fzs-600-fazer-00-fuel-pump_W0QQitemZ250559832283QQcmdZViewItem?rvr_id=&rvr_id=&cguid=6d2769071260a0e2048322d3fffcee00
this needs to be running or you will be riding the bike on gravity fed fuel and as soon as you open the bike up you will not get enough to the engine and will cut out hope this helps