Q. What is the difference between FZ FI and FZ S FI?

Technically there is no differences between them, power and torque figures are same in both the bikes as they both shares same engine, the difference is only in styling FZS comes with chrome detailing, engine guard, a small headlamp visor and some extra graphics and color schemes but on the other side FZ has limited colors available and also doesn't have chrome detailing headlamp visor engine guard.

Fz fi comes without any chrome details and it doesn't have engine guard which fz s fi has other than that there is no diff

Just few of the cosmetic changes like additional visor above head lamp etc. for better visual appeal and aerodynamic nothing significant. Rest everything is same. Same engine and performance.