Haynes manual says NGK CR8E for FZS600.
Or Nippondenso U24ESR-N, which sounds a lot like your current plug.
Incidentally the CR9E is recommended for YZF 600 covered by same manual.
Or Nippondenso U24ESR-N, which sounds a lot like your current plug.
Incidentally the CR9E is recommended for YZF 600 covered by same manual.