Troy-Bilt TB138PS Operator's Manual page 6

MAINTENANCE AND REPAIR INSTRUCTIONS
INSTALLING A PREWOUND REEL
1. Hold the outer spool with one hand and unscrew the
bump knob counterclockwise (Fig. 21). Inspect the bolt
inside the bump knob to make sure it moves freely.
Replace the bump knob if damaged.
2. Remove the old inner reel from the outer spool (Fig. 22).
3. Remove the spring from the old inner reel (Fig. 22).
4. Place the spring in the new inner reel.
NOTE: The spring must be assembled on the inner reel
before reassembling the cutting attachment.
5. Insert the ends of the line through the eyelets in the
outer spool (Fig. 29).
6. Place the new inner reel inside the outer spool. Push the
inner reel and outer spool together. While holding the
inner reel and outer spool, grasp the ends and pull firmly
to release the line from the holding slots in the spool.
7. Hold the inner reel in place and install the bump knob by
turning clockwise. Tighten securely.
POLE SAW MAINTENANCE AND REPAIR
ADJUSTING THE CHAIN TENSION
WARNING:
To avoid possible serious injury,
never touch or adjust the chain while the motor
is running. The saw chain is very sharp; always
wear protective gloves when performing
maintenance on the chain.
WARNING:
A chain tensioned while warm,
may be too tight upon cooling. Check the
"cold tension" before next use.
The chain must be tensioned whenever the flats on the
drive links hang out of the bar groove (Fig. 30). Check for
proper chain tension before starting the unit and
periodically during operation.
NOTE: A new chain tends to stretch. Check the chain
tension frequently and tighten as required.
1. Stop the motor and disconnect the unit from the power
source. Refer to Disconnecting the Power Source in the
Assembly Instructions section.
2. Slightly loosen the bar retaining nuts (Fig. 31 B).
3. Rotate the chain-tensioning screw (Fig. 31 A) clockwise
with a standard screwdriver to tension the chain. The
desired tension depends on the temperature of the chain:
• Cold Chain Tensioning - A cold chain is correctly
tensioned when there is no sag on the underside of the
guide bar and the chain seats snugly against the guide
bar with the drive links in the bar groove.
• Warm Chain Tensioning - During normal operation, the
temperature of the chain will increase. The drive links of a
correctly tensioned warm chain will hang approximately
1/16 inch (1.3 mm) out of the bar groove (Fig. 32).
4. Once adjusted, lift the tip of the guide bar up to check
for proper tension (Fig. 33). If the chain is still too loose,
release the tip of the guide bar and turn the chain-
tensioning screw 1/2 turn clockwise. Repeat this
process until the desired tension is achieved.
NOTE: If the chain is too tight, it will not rotate. To loosen
the chain, turn the chain tensioning screw 1/4
turn counterclockwise. Ensure that the chain can
be turned by hand without binding (Fig. 34). Also
note that the chain will not rotate if the chain
brake is engaged.
5. Hold the tip of the guide bar up and securely tighten the
bar retaining nuts.
REMOVING/REPLACING THE GUIDE BAR AND CHAIN
Use only a low-kickback saw chain that has met kickback
performance per ANSI B175.1 for this saw. This fast-cutting
chain provides kickback reduction when properly maintained.
NOTE: When replacing the guide bar and chain, use only
manufacturer suggested replacement parts. The
use of any other parts may create a hazard or
cause product damage and will VOID the warranty.
Removing the Old Guide Bar and Chain
1. Make sure the motor is OFF and disconnect the unit
from the power source.
2. Rotate the bar retaining nuts counterclockwise and
remove the bar retaining nuts. Using a standard
screwdriver, rotate the bar cover screw counterclockwise
(Fig. 31). Remove the bar cover screw and bar cover.
3. Using a standard screwdriver, rotate the chain-
tensioning screw counterclockwise 4 turns to loosen the
chain. See Adjusting the Chain Tension instructions.
4. Remove the guide bar and chain from the mounting surface.
5. Remove the old chain from the guide bar.
Installing the New Guide Bar and Chain
1. Lay out the new saw chain in a loop and straighten any
kinks. The cutters on the top of the guide bar should face
toward the guide bar tip in the direction of chain rotation
(Fig. 35). If they face backward, turn the loop over.
2. Place the chain drive links into the bar groove as shown
(Fig. 36).
NOTE: Make sure the chain is correctly installed and the
cutters are facing in the correct direction (Fig. 35).
3. Position the chain so there is a loop at the back of the
guide bar.
4. Hold the chain in position on the guide bar and place the
loop around the drive sprocket.
5. Fit the guide bar flush against the mounting surface so
that the bar retaining bolts are in the slot (Fig. 37).
6. Adjust the chain tension. Refer to the Adjusting the
Chain Tension instructions above.
7. Replace the bar cover and bar retaining nuts. To tighten,
rotate the bar retaining nuts clockwise.
NOTE: When replacing the bar cover and bar retaining
nuts, ensure that the chain-tensioning pin is in
the chain-tensioning pin hole (Fig. 37).
6
Loop
Fig. 27
Holding Slots
Fig. 28
Spring
Fig. 29
Flats
Bar Tip
Fig. 30
A
B
Bar
Cover
Bar
Bar
Chain-
Cover
Tensioning Retaining
Screw
Screw Nuts
Fig. 31
Approx 1/16"
(1.3 mm)
Bar Tip
Fig. 32
Fig. 33
Fig. 34
Cutters
Chain
Rotation
Chain Drive
Links
Fig. 35
Bar Groove
Chain
Drive Links
Fig. 36
MAINTENANCE AND REPAIR INSTRUCTIONS
CHAIN MAINTENANCE
WARNING:
A dull or improperly sharpened
chain can cause excessive motor speed during
cutting, which may result in severe motor
damage.
WARNING:
Improper chain sharpening
increases the potential of kickback. Failure to
replace or repair a damaged chain can cause
serious injury.
For smooth and fast cutting, the chain needs to be
maintained properly. The following conditions indicate that
the chain requires sharpening:
• Wood chips are small and powdery.
• The chain must be forced through the wood during cutting.
• The chain cuts to one side.
During maintenance of the chain, consider the following:
• The depth gauge (or raker clearance) setting determines
the height at which the cutter enters the wood and the
size of the wood chip that is removed (Fig. 38). Too much
clearance increases the potential for kickback. Too little
clearance decreases the size of the wood chip, thus
decreasing the chain's cutting ability.
• If the cutter teeth have hit hard objects, such as nails and
stones, or were abraded by mud or sand on the wood,
have a service dealer sharpen the chain.
NOTE: Inspect the drive sprocket for wear or damage
when replacing the chain. If signs of wear or
damage are present in the areas indicated, have
the drive sprocket replaced by an authorized
service center.
NOTE: If you do not fully understand the correct
procedure for sharpening the cutters after
reading the instructions that follow, have the saw
chain sharpened by an authorized service center
or replace the chain with a recommended low-
kickback chain.
SHARPENING THE CUTTERS
Be careful to file all cutters to the specified angles and to
the same length. Fast cutting can be obtained only when all
cutters are uniform.
• Tighten the chain tension enough so that the chain does
not wobble. Do all of the filing at the midpoint of the
guide bar. Wear gloves for protection.
• Use a round file and holder.
• Keep the file level with the top plate of the tooth (Fig. 39).
Do not let the file dip or rock.
• Using light but firm pressure, stroke towards the front
corner of the tooth (Fig. 40). Lift the file away from the
cutter before returning the file to the beginning of the
sharpening stroke.
• Put a few firm strokes on every tooth. File all left hand
cutters in one direction (Fig. 41). Then move to the other
side and file the right hand cutters in the opposite
direction (Fig. 41). Occasionally remove filings from the
file with a wire brush.
Top Plate Filing Angle
• CORRECT (30°) – File holders are marked with guide
marks to align the file properly and produce the correct
top plate angle (Fig. 42).
• INCORRECT (LESS THAN 30°) – For cross cutting (Fig. 43).
• INCORRECT (MORE THAN 30°) – This creates a
feathered edge that dulls quickly.
Side Plate Filing Angle
• CORRECT (80°) – This is produced automatically if the
correct diameter file is used in the file holder (Fig. 42).
• INCORRECT (HOOK) – This causes the chain to "grab"
and dull quickly, increasing the potential for kickback. A
hook is caused by using a file with too small a diameter
or a file held too low (Fig. 43).
• INCORRECT (BACKWARD SLOPE) – This causes a need
for too much feed pressure, producing excessive wear to
the bar and chain. A backward slope is caused by using
a file with too large a diameter or a file held too high.
MAINTAINING DEPTH GAUGE CLEARANCE
• Maintain the depth gauge at a clearance of 1/32" (0.6
mm). Use a depth gauge tool for checking the depth
gauge clearances. (Fig. 38)
• Every time the chain is filed, check the depth gauge
clearance.
• Use a flat file and a depth gauge jointer to lower all
gauges uniformly (Fig. 44). Use a 1/32 inch (0.6 mm)
depth gauge jointer. After lowering each depth gauge,
restore the original shape by rounding the front (Fig. 45).
Be careful not to damage adjoining drive links with the
edge of the file.
• Depth gauges must be adjusted with the flat file in the
same direction the adjoining cutter was filed with the
round file.
• Use care not to contact the cutter face with the flat file
when adjusting depth gauges.
Drive Sprocket
Bar Retaining Bolts
Slot
Chain-Tensioning
Pin Hole
Fig. 37
Raker Clearance
1/32" (0.6 mm)
Cutting Corner
Side Plate
Top Plate
Depth
Gauge
Gullet
Fig. 38
Filing Height
Fig. 39
Filing Angle
Fig. 40
Left Hand
Cutters
Right Hand
Cutters
Fig. 41
Correct
30˚
Filing Angles
Top Plate
80˚
Side Plate
Fig. 42
Incorrect Less Than 30˚ More Than 30˚
Filing Angles
Top Plate
Hook Backward Slope
Side Plate
Fig. 43
Depth Gauge Jointer
Flat File
Fig. 44
Restore Original
Shape by Rounding
the Front
Fig. 45