Yamaha YZF-R125 Service Manual: 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 shown.
c. Measure the spark plug cap resistance.
Checking the diode
1. Check:
Diode
Out of specification Replace.
NOTE:
The pocket tester or the analog pocket tester
readings are shown in the following table.
a. Disconnect the diode from the wire harness.
...
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 ...
Other materials:
Checking the starter motor
1. Check:
Commutator
Dirt Clean with 600 grit
sandpaper.
2. Measure:
Commutator diameter "a"
Out of specification Replace
the starter
motor.
3. Measure:
Mica undercut "a"
Out of specification Scrape
the mica to the
proper measurement with a hacksaw blade
...
Removing the lower bracket
1. Stand the vehicle on a level surface.
WARNINGSecurely support the vehicle so that there
is
no danger of it falling over.
2. Remove:
Upper ring nut
Rubber washer
Lower ring nut "1"
Lower bracket
NOTE:
Remove the lower ring nut with the steering nut
wrench "2".
...
Drive chain slack
The drive chain slack should be
checked before each ride and adjusted
if necessary.
To check the drive chain slack
Place the motorcycle on the sidestand.
TIP
When checking and adjusting the drive
chain slack, there should be no weight
on the motorcycle.
Shift the transmission in ...