Yamaha YZF-R125 Service Manual: Checking the ignition coil

1. Check:

Primary coil resistance Out of specification  Replace.


a. Disconnect the ignition coil connectors from the ignition coil terminals.

b. Connect the pocket tester ( × 1)
to the ignition coil as shown.


Positive tester probe
red/white "1"

Negative tester probe
orange "2"

Checking the ignition coil


c. Measure the primary coil resistance.

2. Check:

Secondary coil resistance Out of specification Replace.


 a. Disconnect the spark plug cap from the ignition coil.

b. Connect the pocket tester ( ×
1k) to the ignition coil as shown.


  • Positive tester probe
    orange "1"
  • Negative tester probe
    spark plug lead "2"

Checking the ignition coil


c. Measure the secondary coil resistance.

    Checking the spark plug cap
    1. Check: Spark plug cap resistance Out of specification Replace. a. Remove the spark plug cap from the spark plug lead. b. Connect the pocket tester ( × 1k) to the spark plug cap as ...

    Checking the ignition spark gap
    1. Check: Ignition spark gap Out of specification Perform the ignition system troubleshooting, starting with step 5. Refer to "TROUBLESHOOTING" on page 8-3. NOTE: If the ignition spark gap ...

    Other materials:

    Checking the speed sensor
    1. Check: Speed sensor output voltage Out of specification → Replace. a. Connect the pocket tester (DC 20 V) to the speed sensor coupler (wire harness end) as shown. Positive tester probe gray "1" Negative tester probe gray/black "2" b. Set the main switch to "ON". c. ...

    Checking the rear brake caliper
    1. Check: Brake caliper piston "1" Rust/scratches/wear Replace the brake caliper piston. Brake caliper cylinder "2" Scratches/wear Replace the brake caliper assembly. Brake caliper body "3" Cracks/damage   Replace the brake caliper assembly. Brake fluid deli ...

    Installing the piston and cylinder
    1. Install: Top ring "1" 2nd ring "2" Oil ring expander "3" Lower oil ring rail "4" Upper oil ring rail "5" NOTE: Be sure to install the piston rings so that the manufacturer marks or numbers face up. 2. Install: Piston "1" Piston pin "2" Piston pin clips "3" NOTE: ...

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