This is going to sound idiotic (hopefully no hate mail coming my direction).... However, if all other possible simple solutions don't work, I'd try squirting a few very short squirts of Tri Flow lubricant (not WD-40) down into the ignition switch (where the key is inserted). Then work the key in and out a few times and turn the key back and forth a few times. I'm told by a very reputable locksmith that Tri Flow will not harm the ignition switch in any way. Again, it will sound idiotic to some folks but **** it's worth a try. This technique worked on two of my older, gen 1 FZ1 bikes in the past when they would stall for no apparent reason on occasion after shutting off the bike then and restarting it.