These older Power Base units used a weaker motor which used 3/16" diameter belts and the motor mount holding the motor was positioned in a forward position because the motor shaft was shorter on these older motors. When upgrading to the new R-19 High Torque motor (the replacement motor that has been used on all Power Bases produced since 2011), the user will have to move the gray motor bracket back 1/2" (away from the front of the unit). The larger metal pulley that must be used on the motor when the R-19 is installed, will fit correctly if the motor bracket is moved back one half inch. Alternatively, the bracket may be left as is but the pulley needs to be installed in reverse (with the pulley groove next to motor housing and the hub with the set screw at the end of the shaft).
If you have questions about these instructions, please call Bob at NKK (800-731-5648).