Fasten The Rail To The Motor Unit; Install The Idler Pulley - Chamberlain WHISPER DRIVE Security+ HD900D Owner's Manual

ASSEMBLY STEP 2

Fasten the Rail to the Motor Unit

• Insert a 1/4"-20x1-3/4" bolt into the cover protection bolt hole
on the back end of the rail as shown. Tighten securely with a
1/4"-20 lock nut. DO NOT overtighten.
• Remove the two bolts from the top of the motor unit.
• Place the "U" bracket, flat side down, on the motor unit and
align the bracket holes with the bolt holes. Fasten with the
previously removed bolts.
• Align the rail assembly with the top of the motor unit. Slide the
rail end onto the "U" bracket, all the way to the stops that
protrude on the top and sides of the bracket.
HARDWARE SHOWN ACTUAL SIZE
Bolt 1/4"-20x1-3/4"
ASSEMBLY STEP 3

Install the Idler Pulley

• Lay the belt beside the rail, as shown. Grasp the end with the
hooked trolley connector and pass approximately 12" (30 cm)
of belt through the window. Keep the ribbed side toward the
rail, and allow it to hang until Assembly Step 5.
• Remove the tape from the idler pulley. The inside center should
be pre-greased. If dry, regrease to ensure proper operation.
• Place the idler pulley into the window as shown.
• 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.
• Rotate the pulley to be sure it spins freely.
• Insert a 1/4"-20x1-3/4" bolt into the trolley stop hole in the
front of the rail as shown. Tighten securely with a 1/4"-20
lock nut.
Idler Bolt
To avoid SERIOUS damage to garage door opener, use ONLY
those bolts/fasteners mounted in the top of the opener.
Lock Nut
1/4"-20
Lock Washer 3/8"
HARDWARE SHOWN ACTUAL SIZE
Bolt 1/4"-20x1-3/4"
9
Bolts
"U" Bracket
Bolt
Cover
Protection
Bolt Hole
SLIDE RAIL TO
STOPS ON TOP
AND SIDES
Lock Nut OF BRACKET
Pulley
Screwdriver
Idler Bolt
Nut 3/8"
Trolley
Connector
Lock Nut 1/4"-20 Nut 3/8"
Motor Unit
Belt Pulley
Bolt
Rail
Nut
Washer
Bolt
Trolley
Stop Hole
Grease
Inside Pulley
Idler Pulley
Idler
Lock
Pulley
Nut
Lock Washer 3/8"