Yamaha YB50 Service Manual page 136

3. Spark plug cap resistance
• Remove spark plug cap
• Connect the pocket tester (Ωx1k) on the
spark plug cap.
• Check if the spark plug pipe has the spe-
cified resistance
Resistance of spark plug:
5 kΩ at 20 °C (68 °F)
4. Resistance of ignition coil
• Disconnect the ignition coil cables.
• Connect the pocket tester (Ωx1) on the
ignition coil .
Ignition coil:
Cable (+) of tester
(orange)
Cable (–) of tester
(ground)
• Check if the primary coil has the specified
resistance.
Primary coil resistance:
0.56 ~ 0.84 Ω at 20 °C (68 °F)
• Connect the pocket tester (Ωx1k) on the
ignition bobbin.
Cable (+) of tester
plug
Cable (–) of tester
• Check if the secondary coil has the speci-
fied resistance.
Secondary coil resistance:
5.7 ~ 8.5 kΩ at 20 °C (68 °F)
(Spark plug cable - Coil cable)
IGNITION AND STARTER SYSTEM
SATISFIES
THE
SPECIFIED
VALUE
Terminal +
Terminal –
Cable of spark
Ground
BOTH SATISFY
THE SPECIFIED
VALUE
OUTSIDE SPECIFIED VALUE
Replace the spark plug cap
OUTSIDE SPECIFIED VALUE
The ignition coil is defective, replace it
7-6
ELEC