ESF905 is a brand new replacement rotor for the alternator system on CB1100F. The Honda OEM rotors of these years are prone to failure and ElectroSport developed a high quality replacement rotor for these models. This rotor is a direct replacement for the OEM rotor, and it comes with a full one year warranty. Check the OEM rotor resistance between the slip rings with a multimeter: if it is less than 4.3 Ohms you can be sure that the rotor is bad. Typical symptom: no charge to the battery. Often when the rotor fails due to internal shorting (resistance less than 2 Ohms) it will take out the voltage regulator/rectifier. Check on our ESR210 regulator/rectifier applications.