Replacing The Spark Plug - MTD T/120 User Manual

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.
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.
Adjust Idle Speed Adjuster
If after checking the fuel mixture and cleaning the air
filter the engine
still will not idle, adjust the idle speed adjuster as
follows.
1. Start the engine and let it run about 2–3 minutes at a
high speed (full throttle) to warm up.
NOTE: Ensure the tines are not in contact with the
ground when adjusting the idle.
2. Release the throttle trigger and let the engine idle. If
the engine stops, insert a small phillips into the hole
in the air filter/muffler cover (Fig. 18). Turn the idle
speed adjuster in, clockwise, 1/8 of a turn at a time
(as needed) until the engine idles smoothly.
NOTE: The tines should not rotate when the engine
idles.
3. If the tines rotate when the engine idles, turn the idle
speed adjuster counterclockwise 1/8 of a turn at a
time (as needed), to reduce idle speed.
Checking the fuel mixture, cleaning the air filter, and
adjusting the idle
speed screw should solve most engine problems.
MAINTENANCE AND REPAIR INSTRUCTIONS
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.

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 50 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.
3. Replace cracked, fouled or dirty spark plug. Set the
air gap at 0.5 mm (0.020 in.) using a feeler gauge
(Fig. 19).
4. Install a correctly gapped spark plug in the cylinder
head. Tighten by turning the 5/8 in. socket clockwise
until snug.
Do not over tighten.
CLEANING
Use a small brush to clean off the outside of the unit. Do
not use strong detergents. Household cleaners that
contain aromatic oils
such as pine and lemon, and solvents such as kerosene,
can damage plastic housing or handle. Wipe off any
moisture with a soft cloth.
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