Chamberlain 2500B - Manual (Page 6)

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 two washered bolts mounted in top of
motor unit.
• Align rail and styrofoam over sprocket. Cut tape
from rail, belt and styrofoam.
• REMOVE STYROFOAM.
• Insert both washered bolts through the rail into the
motor unit. Tighten bolts securely.
Use only these bolts! Use of any other bolts
will cause serious damage to door opener.
• Position belt over the motor unit sprocket.
6
Motor Unit
Sprocket
Foam Packaging
Washered Bolts
5/16"-18x1/2"
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
Trolley
Nut
Ring
Trolley
Threaded
Shaft
Nut Ring
Slots
Trolley
Square End Figure 1
Figure 2
Nut Ring Trolley Nut Ring Trolley
1" 1-1/4"
BEFORE AFTER RELEASE
Figure 3
To avoid SERIOUS damage to garage door opener,
use ONLY those bolts/fasteners mounted in the top of
the opener.
WARNING
CAUTION WARNING
WARNING