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To avoid SERIOUS damage to opener, ONLY use bolts/
fasteners mounted in top of motor unit.
ASSEMBLY STEP 2
Set the Belt Tension
• By hand, thread the spring trolley nut on the threaded
shaft until it is finger tight against the trolley (Figure 1).
Do not use any tools.
• Insert a screwdriver tip into one of the nut ring slots
and brace it firmly against the trolley (Figure 2).
• Place a 7/16" open end wrench on the square
end. Rotate about 1/4 turn until the spring releases and
snaps the nut ring against the trolley (Figure 3).
This extends the spring for optimum belt tension.
Trolley
Threaded
Shaft
Spring/Trolley Nut
The Chamberlain Group, Inc.
Liftmaster Synchro Drive
Spring Trolley Nut Assembly
3/5/92 - 5/16 /92 - 5/21/92 - 6/2/92
6/11/92
Nut
Ring
Trolley
Threaded
Shaft
Nut Ring
Slots
Square
End
Nut Ring Trolley
Nut Ring
Trolley
1" (2.5 cm) 1-1/4" (3.18 cm)
BEFORE AFTER RELEASE
Figure 1
Figure 2
Figure 3
ASSEMBLY STEP 1
Attach the Rail to the Motor Unit
To avoid installation difficulties, do not run the
garage door opener until instructed to do so.
• Remove the bolt and lock nut from the top of the motor
unit.
• Place rail onto the bolt mounted on the motor unit and
align the back hole with the hole in the top of the unit.
• Fasten rail with the washered bolt and lock nut
previously removed. Tighten securely. Remember to
use only these bolts/fasteners! Any other bolts/
fasteners will cause serious damage to the opener.
• Cut tape from rail, belt and styrofoam.
• REMOVE STYROFOAM.
• Position belt over the motor unit sprocket.
Motor unit
Sprocket
Washered Bolt
5/16"-18x1/2"
Styrofoam
Rail
Hole
Lock Nut
USE ONLY THIS
TYPE AND SIZE
BOLT