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CAUTION: Do not sand blast, scrape, or clean
electrodes. Grit in the engine could damage the
cylinder.
4. Install a correctly gapped spark plug in the cylinder
head. Tighten by turning the 5/8 in. socket clockwise
until snug.
If using a torque wrench torque to:
12.3-13.5 N•m (110-120 in.•lb.)
Do not over tighten.
FIGURE 39
REPLACING THE SPARK PLUG
Use a Champion RDJ7Y spark plug (or equivalent). The
correct air gap is 0.5 mm (0.020 in.). Remove the plug
after every 25 hours of operation and check its condition.
1. Stop the engine and allow it to cool. Grasp the plug
wire firmly and pull the cap from the spark plug.
2. Clean dirt from around the spark plug. Remove the
spark plug from the cylinder head by turning a
5/8 in. socket counterclockwise.
NOTE: Replace cracked, fouled or dirty spark plug.
3. Set the air gap at 0.5 mm (0.020 in.) using a feeler
gauge, Figure 39.
0.5 mm
(0.020 in.)
Checking the fuel mixture, cleaning the air filter, and
adjusting the idle speed should solve most engine
problems.
If not and:
• 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.
WARNING: When the unit is turned off make
sure the cutting head has stopped before the
unit is set down to prevent serious personal
injury.
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
and change the air/fuel mixture. 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.
Adjusting the Idle Speed
WARNING: The cutting head will spin during
idle speed adjustments. Wear protective
clothing and observe all safety instructions to
prevent serious personal injury.
If after checking the fuel mixture and cleaning the
air filter the engine still will not idle, adjust the idle speed
as follows.
1. Start the engine and let it run at a high idle for a
minute to warm up. See Starting/Stopping
Instructions.
2. Release the throttle trigger and let the engine idle. If
the engine stops, insert a small phillips or flat blade
screwdriver into the hole in the air filter/muffler
cover, Figure 38. Turn the idle speed screw in,
clockwise, 1/8 of a turn at a time (as needed) until
the engine idles smoothly.
3. If the engine appears to be idling too fast, turn the
idle speed screw out, counterclockwise, 1/8 of a
turn at a time (as needed) to reduce idle speed.
NOTE: If a tachometer is available, set idle speed to
RPM specifications in Specifications section.
FIGURE 38
Idle Speed Screw
CARBURETOR ADJUSTMENT
The idle speed of the engine is adjustable through the
air filter/muffler cover, Figure 38.
NOTE: Careless adjustments can seriously damage
your unit. An authorized service dealer should
make carburetor adjustments.
Check Fuel Mixture
Old and/or improperly mixed fuel is usually the reason
for the unit not running properly. Drain and refill the tank
with fresh, properly mixed fuel prior to making any
adjustments. Refer to Oil and Fuel Information.