The black box fails very rarely, I would push it to the end of the list.
As mentioned before, the ignition barrel is the prime suspect. Same for its cables and plugs. Also remove the protection hosing of the cables, sometimes the cables are fried inside.
Disassemble the barrel and clean the contact plate. The WD40 solution is only temporary.
Second the ignition coils. They might get cracks in the plastic and the spark goes elsewhere. Inspect in the dark and look for discharge/arcs to the frame. Same for the spark caps and cables.
ECU at the end. First swap with a borrowed good one from a friend.
The sticker:
fzs1000
2001 5LV-82305-00
2002 5LV-82305-00
2003 5LV-82305-40 no headlight switch, controlled by ECU
2004 5LV-82305-40
2005 1C2-82305-00
All US models
Fzs1000 & FZS1000s 2001- 2005 5LV-82305-30
Use the 2001, 2002 EU model, matches best to your bike. Newer ones might make trouble with the headlights.
Edit: Assumed your bike is 2001.
As mentioned before, the ignition barrel is the prime suspect. Same for its cables and plugs. Also remove the protection hosing of the cables, sometimes the cables are fried inside.
Disassemble the barrel and clean the contact plate. The WD40 solution is only temporary.
Second the ignition coils. They might get cracks in the plastic and the spark goes elsewhere. Inspect in the dark and look for discharge/arcs to the frame. Same for the spark caps and cables.
ECU at the end. First swap with a borrowed good one from a friend.
The sticker:
fzs1000
2001 5LV-82305-00
2002 5LV-82305-00
2003 5LV-82305-40 no headlight switch, controlled by ECU
2004 5LV-82305-40
2005 1C2-82305-00
All US models
Fzs1000 & FZS1000s 2001- 2005 5LV-82305-30
Use the 2001, 2002 EU model, matches best to your bike. Newer ones might make trouble with the headlights.
Edit: Assumed your bike is 2001.