Yamaha YFM660RN Service Manual page 290

Connect the pocket tester (Ω × 1k) to the
ignition coil.
Tester (+) lead → Orange lead terminal
Tester (–) lead → Spark plug lead
Check that the secondary coil has the
specified resistance.
Secondary coil resistance:
6.32 ~ 9.48 kΩ at 20 °C (68 °F)
7.Engine stop switch
Refer to "CHECKING THE SWITCH".
8.Main switch
Refer to "CHECKING THE SWITCH".
9.Pickup coil resistance
Disconnect the AC magneto coupler from
the wire harness.
Connect the pocket tester (Ω × 100) to the
pickup coil terminal.
Tester (+) lead → White/Red terminal 1
Tester (–) lead → White/Green terminal 2
Check the pickup coil for the specified
resistance.
Pickup coil resistance:
445 ~ 545 Ω at 20 °C (68 °F)
(White/Red – White/Green)
*
BOTH MEET
SPECIFICATION
CORRECT
CORRECT
MEETS
SPECIFICATION
8 - 9
IGNITION SYSTEM
Replace the ignition coil.
INCORRECT
Replace the handlebar switch (left).
INCORRECT
Replace the main switch.
OUT OF SPECIFICATION
Replace the pickup coil/starter assembly.
– +
ELEC