Idle Speed Adjustment; Rocker Arm Clearance - Craftsman 79193 - Straight Shaft Trimmer Operator's Manual

iDLE SPEED ADJUSTMENT
The idle speed of the engine is adjustable. An idle adjustment screw
is between the air filter cover and the engine starter housing (Fig. 28).
NOTE: Careless adjustments can seriously damage the unit. Aside
from idle speed, only a Sears or other qualified service
dealer should make carburetor adjustments.
First, Check Fuel
Old fuel is usually the reason for improper unit performance. Drain
and refill the tank with fresh fuel prior to making any adjustments.
Refer to Oil and Fuel Information.
Second, Clean Air Filter
The condition of the air filter is important to the operation of the unit.
A dirty air filter will restrict air flow. This is often mistaken for an out
of adjustment carburetor. Check the condition of the air filter before
adjusting the idle speed screw. Refer to Air Filter Maintenance.
Third, Adjust Idle Speed Screw
_WARNING:
The cutting attachment may spin during idle
speed adjustments. Wear protective clothing and observe I
all safety instructions to prevent serious personal injury, j
If, after checking the fuel and Idle Adjustment
cleaning the air filter, the Screw
engine still will not idle, adjust
the idle speed screw as
follows:
1.
Start the engine and let it
run at a high idle for a
minute to warm up. Refer
to Starting/Stopping
Instructions.
Fig. 28
2. Release the throttle trigger and let the engine idle. If the engine
stops, insert a small phillips in between the Air Filter Cover and
the Engine Cover (Fig. 28). Turn the idle speed screw in,
clockwise, 1/8 of a turn at a time (as needed) until the engine
idles smoothly.
NOTE: The cutting attachment should not rotate when the engine
idles.
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 any of the following are
true have the unit serviced by a Sears or other qualified service dealer:
• the engine will not idle
the engine hesitates or stalls on acceleration
there is a loss of engine power
ROCKER ARM CLEARANCE
WAR N IN G:
To avoid serious personal injury, a lways turn your I
trimmer off and allow it to cool before you clean or maintain it. J
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 dealer.
NOTE: inspect the valve to rocker arm clearance with a feeler
gauge after the first 10 hours of operation and every 25
hours of operation. View of the Rear Engine Cover
, The engine must be cold
when checking or adjusting
the valve clearance. Screws Screws
This task should be
performed inside, in a clean,
dust free area.
1. Remove the six (6) screws
on the back of the engine
cover with a Flat-head or
T-25 Torx screwdriver (Fig. 29).
2. Disconnect the spark plug wire.
Fig. 29
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. Remove the engine cover (Fig. 29).
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. 30). 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. 30)
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 valve return
spring. Measure the
clearance between the
valve stem and rocker
arm (Fig. 32). Measure
SC few ------_}B_
RockerArm
Cover
Spark
Plug Hole
Fig. 30
iNTAKE
Rocker
Arms
Adjusting Nuts
EXHAUST
Fig. 31
Exhaust Rocker Arm
Adjusting "-_---_J_ / Feeler
Nut _ Gauge
0.003-0.006 in__ _
(0.076-0.152 ram)
Valve Stem
Fig. 32
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. See Figures 31
and 32.
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. 32).
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.
9