Stihl 064

STIHL 064, 066 47
Checking the spark plug: Warning: Do not touch any live Note: Chafed insulation on the ig-
parts - contact with high voltage nition lead or short circuit wire will
Accurate checking of the spark can cause serious or fatal acci- cause a short-circuit to ground. In
plug is only possible with a special dents! this case the engine with either not
spark plug tester. start or only run erratically.
Note: It is recommended that a
A provisional check can be carried new spark plug be fitted in all To install the spark plug:
out by fitting a clean spark plug in cases of doubt.
the spark plug terminal and hold- - Clean the spark plug seat and fin-
ing it against ground. There should If there is no sparkover even spect the sealing ring to make
be a powerful sparkover at the though the spark plug is in good sure it is in good condition.
electrodes when the engine is condition, first check the lead con -
cranked by pulling the starter rope. nections. - Fit the spark plug and tighten it
down to a torque of 25 Nm (18.5
Ibf.ft).
The appearance of the spark plug's insulator nose gives valuable information with regard to the effects of various operating
conditions:
Condition of Insulator Nose Appearance Meaning
Normal: Grayish yellow-to-brown, dry Engine in order, correct spark
as specified plug (heat range)
Sooted: Velvet-like, dull black coating Mixture too rich, lack of air
of soot (dirty air filter, choke shutter
partly closed),
electrode gap too wide, wrong
spark plug (heat range too high)
Smeared with oil: Coating of damp oil Too much oil in fuel mix
carbon and soot
Overheated: Welding beads on insulator Mixture too lean, spark plug loose,
nose, pitted electrodes wrong spark spark plug
(heat range too low) (heat range too low)