the FZ6 like the R6 and the R1 have a built in diagnostic feature that allows you to test all the electronics of the bike. even the battery voltage. no need for any diagnostic equipment on a Yamaha. the first thing you need to check is your charging voltage while the engine is running. it needs to be at least 14v @ 5k rpm at minimum. (should actually be 14 at an idle) if it isn't, don't assume you need to buy stuff. next unplug the rectifier and look closely at the connectors and the wires. a lot of yamaha's have had problems with the connectors. if it's fine move on. test resistance of the stator with a multimeter. this is from a R6. the plug shape might be different but that doesn't matter.