Step 4: Arm Attachment - Chamberlain LiftMaster BG770 Installation And Maintenance Manual

Arm Attachment
Step 4:
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.
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.
MODEL BG770: STANDARD ARM
Attach arm to the arm hub flange as shown in Figure 7.
MODEL BG770: OPTIONAL ARM
Attach arm to the arm hub flange as shown in Figure 8.
Gate Arm
Hex Bolt
1/2"-13 x 2-1/4"
Lock Washer & 1/2"-13 Hex Nut
Figure 7
Figure 8
Installation
Hub Flange
01-G0674F9
Doc 01-G0674
14
Rev E