Replacing The Spark Plug; Spark Arrestor Maintenance - Craftsman professional WEEDWACKER 316.791990 Manual De Instrucciones

3. If the cutting attachment rotates when the engine idles, turn the
idle speed screw counterclockwise 1/8 of a turn at a time (as
needed), to reduce idle speed.
Checking the fuel, cleaning the air filter, and adjusting the idle speed
should solve most engine problems. If not and all of the following
are true:
• the engine will not idle
• the engine hesitates or stalls on acceleration
• there is a loss of engine power
Have the carburetor adjusted by an authorized service dealer.
ROCKER ARM CLEARANCE
WARNING:
To avoid serious personal injury, always turn your
trimmer off and allow it to cool before you clean or maintain it.
This requires disassembly of the engine. If you feel unsure or
unqualified to perform this, take the unit to a Sears or other qualified
service center.
NOTE: Inspect the valve to rocker arm clearance with a feeler
gauge after the first 25 hours of operation and then every
25 hours of operation thereafter.
• The engine must be cold when checking or adjusting the valve
clearance.
• This task should be performed inside in a clean, dust free area.
1. Remove the two (2) screws on back of the engine cover and the
one on the front of the engine cover with a Flat-head or T-25
Torx screwdriver (Fig. 27).
2. Remove the engine cover
(Fig. 28).
3. Disconnect the spark plug
wire.
4. Clean dirt from around the
spark plug. Remove the
spark plug from the
cylinder head by turning a
5/8 in. socket
counterclockwise.
5. Clean dirt from around the
rocker arm cover. Remove
the screw holding the
rocker arm cover with a
large flat blade
screwdriver or Torx T-25
bit (Fig. 29). Remove the
rocker arm cover and
gasket.
6. Pull the starter rope
slowly to bring the piston
to the top of its travel,
(known as top dead
center). Check that:
• The piston is at the top of its
travel. This should be done
by looking into the spark
plug hole. (Fig. 29)
• Both rocker arms move
freely, and both valves are
closed
If these statements are
not true, repeat step 6.
7. Slide the feeler gauge
between the rocker arm
and the top of each valve
stem. Measure the
clearance between the valve stem and rocker arm (Fig. 31).
Measure both the intake and exhaust valves.
The recommended clearance for both intake and exhaust is .003 – .006 in.
(.076 – 0.152 mm). Use a standard automotive .005 in. (0.127 mm) feeler
gauge. The feeler gauge should slide between the rocker arm and valve
stem with a slight amount of resistance, without binding. Figure 30 and 31
show how to measure the clearance.
MAINTENANCE & REPAIR INSTRUCTIONS
Remove Screws
Fig. 27
Engine
Cover
Muffler
Fig. 28
Screw
Rocker Arm
Cover
Spark
Plug Hole
Fig. 29
Adjusting Nuts
INTAKE
EXHAUST
Rocker
Arms
Fig. 30
8. If the clearance is not
within specification:
a. Turn the adjusting nut using
a 5/16 inch (8 mm) wrench
or nut driver (Fig. 31).
• To increase clearance,
turn the adjusting nut
counterclockwise.
• To decrease clearance,
turn the adjusting nut
clockwise.
b. Recheck both clearances, and adjust as necessary.
9. Reinstall the rocker arm cover using a new gasket. Torque the
screw to 20–30 in•lb (2.2–3.4 N•m).
10. Check the spark plug and reinstall. See Replacing the Spark Plug.
11. Replace the spark plug wire.
12. Reinstall the engine cover. Check alignment of the cover before
tightening the screws. Tighten screws.

REPLACING THE SPARK PLUG

Use a replacement Champion
gap is 0.025 in. (0.635 mm). Remove the plug after every 25 hours of
operation and check its condition.
1. Stop the engine and allow it to cool. Remove the two (2) screws
on back of the engine cover and the one on the front of the
engine cover with a Flat-head or T-25 Torx screwdriver (Fig. 27).
2. Grasp the plug wire firmly and pull the cap from the spark plug.
WARNING:
Do not sand blast, scrape or clean spark plug
electrodes. Grit in the engine could damage the cylinder.
3. Clean dirt from around the
spark plug. Remove the
spark plug from the
cylinder head by turning a
5/8 in. socket
counterclockwise.
4. Replace cracked, fouled
or dirty spark plug. Set
the air gap at 0.025 in.
(0.635 mm) using a feeler
gauge (Fig. 32).
5. Install a correctly-gapped spark plug in the cylinder head. Turn
the 5/8 in. socket clockwise until snug.
If using a torque wrench, torque to: 110-120 in.•lb. (12.3-13.5 N•m)
Do not over tighten.

SPARK ARRESTOR MAINTENANCE

1. Remove the engine cover.
See Rocker Arm
Clearance.
2. With a flat blade
screwdriver or Torx T-20
bit and a T-25 bit, remove
the screws attaching the
spark arrestor diverter to
the muffler (Fig. 33).
3. Pull the tab on the spark
arrestor cover out of the
muffler. Remove the spark arrestor cover.
4. Remove the spark arrestor screen from the spark arrestor
cover.
5. Clean the spark arrestor screen with a wire brush or replace it.
6. Reinstall the spark arrestor screen, spark arrestor cover and
screw.
9
Exhaust Rocker Arm
Adjusting
Nut
0.003–0.006 in.
(0.076–0.152 mm)
Fig. 31
® RDZ19H spark plug. The correct air
0.025 in.
(0.635 mm)
Fig. 32
Spark Arrestor
Muffler
Screen
Diverter
Slot
T-20 Screw
Fig. 33
Feeler
Gauge
Valve Stem
T-25
Screw