Spark plugs – MTD AC3 User Manual
Page 10
AC3 Series of engines
6
Spark plugs
The spark plug used in the 32cc trimmer is a Cham-
pion RDZ19H gapped to 0.025” (.655 mm).
See Figure 2.3.
Wear rate will vary with severity of use. If the edges of
the center electrode are rounded-off, or any other appar-
ent wear / damage occurs, replace the spark plug before
operating failure (no start) occurs.
Cleaning the spark plug:
NOTE: We do not recommend cleaning spark
plugs.
•
Use of a wire brush may leave metal deposits
on the insulator that causes the spark plug to
short out and fail to spark.
•
Use of abrasive blast for cleaning may cause
damage to ceramic insulator or leave blast
media in the recesses of the spark plug.
•
When the media comes loose during engine operation, severe and non-warrantable engine damage may
result.
Inspection of the spark plug can provide indications of the operating condition of the engine.
•
Light tan colored deposits on insulator and electrodes is normal.
•
Dry, black deposits on the insulator and electrodes indicate an over-rich fuel / air mixture (too much fuel or
not enough air)
•
Wet, black deposits on the insulator and electrodes indicate the presence of oil in the combustion cham-
ber.
•
Heat damaged (melted electrodes / cracked insulator / metal transfer deposits) may indicate detonation.
•
A spark plug that is wet with fuel indicates that fuel is present in the combustion chamber, but it is not
being ignited.
Spark plug removal and installation
To replace a spark plug:
1.
Disconnect the spark plug wire. See Figure 2.4.
2.
Remove the spark plug using a 5/8” spark plug
socket.
3.
Gap a new plug at 0.025” (.6 mm).
4.
Install the spark plug and tighten to a torque of 100 -
110 in. lbs.(11 -12 Nm).
5.
Follow steps 1 and 2 in reverse order.
6.
Test run the trimmer in a safe area before returning it to service.
Figure 2.3
Figure 2.4
Spark plug wire
! CAUTION
! CAUTION
Do not grab the spark plug wire
with pliers. Damage to the spark-
plug boot will result. A damaged
spark plug boot will weaken the spark of the spark
plug.