ESR266 is designed to complement the ESG650 / ESG652 high output stators on the XV650 Yamaha. The OEM regulator/rectifier is not able to handle the extra power from the high output stators properly so we highly recommend replacing the stator and regulator/rectifier as a set on these bikes. ESR266 is a high quality regulator that uses the newest version of our regulator circuits installed in a modern heat sink. Output voltage will be stable across the RPM range and reliability is superb due to the efficient heat sink and top notch materials. We offer ESR266 with a full one year warranty.