Yamaha YFM400FAR Service Manual page 318

Spark plug gap:
0.6 ~ 0.7 mm (0.024 ~ 0.028 in)
4.Ignition spark gap
Disconnect the spark plug cap from the
G
spark plug.
Connect the dynamic spark tester 1 as
G
shown.
2 Spark plug cap
3 Spark plug
Turn the main switch to "ON".
G
Check the ignition spark gap.
G
Crank the engine by pushing the starter
G
switch, and increase the spark gap until a
misfiring occurs.
Minimum spark gap:
6.0 mm (0.24 in)
5.Spark plug cap resistance
Remove the spark plug cap.
G
Connect the pocket tester (Ω × 1k) to the
G
spark plug cap.
Check that the spark plug cap has the
G
specified resistance.
Spark plug cap resistance:
10 kΩ at 20 °C (68 °F)
*
CORRECT
OUT OF
SPECIFICATION
OR NO SPARK
MEETS
SPECIFICATION
9 - 11
IGNITION SYSTEM
INCORRECT
Repair or replace the spark plug.
MEETS SPECIFICATION
The ignition system is not faulty.
OUT OF SPECIFICATION
Replace the spark plug cap.
– +
ELEC