Yamaha YFM250XL(C) Service Manual page 293

Start the engine and accelerate to about
2,000 r/min.
Charging voltage:
14 to 15 V at 2,000 r/min
NOTE:
Use a fully charged battery.
EB804012
4.Stator coil resistance
Disconnect the AC magneto coupler
from the wire harness.
Connect the pocket tester (Ω × 1) to the
stator coils.
Tester (+) lead → White terminal 1
Tester (–) lead → White terminal 2
Tester (+) lead → White terminal 1
Tester (–) lead → White terminal 3
Measure the stator coil resistance.
Stator coil resistance:
0.45 ~ 0.55 Ω at 20 ˚C (68 ˚F)
EB804015
5.Wiring connections
Check the connections of the entire
charging system.
Refer to "CIRCUIT DIAGRAM".
Replace the rectifier/regulator.
CHARGING SYSTEM
OUT OF
SPECIFICATION
MEETS
SPECIFICATION
CORRECT
8 - 23
MEETS SPECIFICATION
The charging circuit is not faulty.
OUT OF SPECIFICATION
Replace the stator coil assembly.
POOR CONNECTION
Properly connect the charging system.
– +
ELEC
8