Craftsman 139.18451DM Manuel D'instructions page 9

ASSEMBLY STEP 2
Fasten the Rail to the Motor Unit
1. Insert a 1/4"-20x2-1/2 bolt, washer and spacer into the cover
protection bolt hole on the back end of the rail as shown. Install
lower spacer and washer then tighten securely with a 1/4"-20
lock nut. DO NOT overtighten.
2. Remove the two bolts from the top of the motor unit.
3. Use the carton to support the front end of the rail.
4. Place the "U" bracket, fl at side down onto the motor unit and
align the bracket holes with the bolt holes. Fasten the "U"
bracket with the previously removed bolts; DO NOT use any
power tools. The use of power tools may permanently damage
the garage door opener.
5. Attach spreader to the motor unit with two screws.
HARDWARE SHOWN ACTUAL SIZE
Lock Nut 1/4"-20
Washer 5/8"
Bolt 1/4"-20x1-1/2"
ASSEMBLY STEP 3
Install the Idler Pulley
1. Lay the chain/cable beside the rail, as shown. Grasp the end of
the cable and pass approximately 12" (30 cm) of cable through
the window. Allow it to hang until Assembly Step 4.
2. Remove the tape from the idler pulley. The inside center should
be pre-greased. If dry, regrease to ensure proper operation.
3. Place the idler pulley into the window as shown.
4. Insert the idler bolt from the top through the rail and pulley.
Tighten with a 3/8" lock washer and nut underneath the rail until
the lock washer is compressed.
5. Rotate the pulley to be sure it spins freely.
6. Locate the rail tab. The rail tab is between the idler bolt and the
trolley in the front rail section. Use a fl at head screwdriver and
lift the rail tab until the tab is vertical (90°).
Spacer
HARDWARE SHOWN ACTUAL SIZE
Idler Bolt
To avoid SERIOUS damage to garage door opener, use ONLY
those bolts/fasteners mounted in the top of the opener.
Hex Screws
8-32x7/16"
Bolt
1/4"-20x2-1/2
"U" Bracket
Washer 5/8"
Spacer
Cover
Protection
Bolt Hole
Spacer
Washer 5/8"
Lock Nut
1/4"-20
Chain and
Cable
Rail
Screwdriver
Tab
Idler
Bolt
Lock
Washer
3/8"
Nut 3/8"
Nut 3/8"
9
Chain
Spreader
Bolt
CORRECT
Rail Tab
INCORRECT
Trolley
Grease
Inside Pulley
Idler
Pulley
Cable Link
Lock Washer 3/8"