LiftMaster BG790 BG790 Manual - Page 8

INSTALLATION ARM ATTACHMENT For easier access during installation, the top cover of the unit may be opened by removing the two wing nuts from underneath, inside the cabinet. MODEL BG770: STANDARD ARM Attach arm to the arm hub flange (Figure 5). MODEL BG770: OPTIONAL ARM Attach arm to the arm hub flange (Figure 6). WARNING When following the procedure below, the motor belt will turn and the drive shaft will move during some of the steps. Keep hands and tools out of the gate cabinet and away from the belt and drive shaft or SERIOUS INJURY may result. Be sure to DISCONNECT power while installing the arm attachment. Figure 5 Gate Arm Hub Flange Hex Bolt 1/2"-13 x 2-1/4" Lock Washer and 1/2"-13 Hex Nut Figure 6 (4) Hex Bolts Extension Arm S Screw Lift Arm See Detail A Hex Bolt (2) Flat Washers DETAIL A See Detail B Threaded Rod Hex Bolt Flat Washer DETAIL B (2) Flat Washers Hex Nut Hex Nut Hex Nut Flat Washer Threaded Spacer Flat Washer Flat Washer Hex Bolt 8