Yamaha YFM660RN Service Manual page 302

Start the engine and accelerate to about
5,000 r/min.
Charging voltage:
14 V at 5,000 r/min
EB804012
4.Charging coil resistance
Disconnect the AC magneto coupler from
the wire harness.
Connect the pocket tester (Ω × 1) to the
charging coils.
Tester (+) lead → White terminal 1
Tester (–) lead → White terminal 2
Tester (+) lead → White terminal 1
Tester (–) lead → White terminal 3
Tester (+) lead → White terminal 2
Tester (–) lead → White terminal 3
Measure the stator coil resistance.
Charging coil resistance:
0.43 ~ 0.65 Ω at 20 °C (68 °F)
EB804015
5.Wiring connections
Check the connections of the entire charg-
ing system.
Refer to "CIRCUIT DIAGRAM".
Replace the rectifier/regulator.
CHARGING SYSTEM
OUT OF
SPECIFICATION
MEETS
SPECIFICATION
CORRECT
8 - 21
MEETS SPECIFICATION
The charging circuit is not faulty.
OUT OF SPECIFICATION
Replace the pickup coil/stator assembly.
POOR CONNECTION
Properly connect the charging system.
– +
ELEC