Yamaha YZF-R125 Service Manual: Checking the relays
Check each switch for continuity with the pocket
tester. If the continuity reading is incorrect, replace
the relay. 
1. Disconnect the relay from the wire harness.
2. Connect the pocket tester ( × 1) and battery (12 V) to the relay terminal as shown.
Check the relay operation.
Out of specification → Replace.
Starter relay
1. Positive battery terminal
2. Negative battery terminal
3. Positive tester probe
4. Negative tester probe
Starting circuit cut-off relay
1. Positive battery terminal
2. Negative battery terminal
3. Positive tester probe
4. Negative tester probe 
Headlight relay
1. Positive battery terminal
2. Negative battery terminal
3. Positive tester probe
4. Negative tester probe 
Radiator fan motor relay
1. Positive battery terminal
2. Negative battery terminal
3. Positive tester probe
4. Negative tester probe
Checking and charging the battery
WARNINGBatteries generate explosive hydrogen gas
and contain electrolyte which is made of poisonous
and highly caustic sulfuric acid.
Therefore, always follow these preventive
mea ...
Checking the turn signal relay
1. Check:
Turn signal relay input voltage
Out of specification →The wiring circuit
from
the main switch to the turn signal relay coupler
is faulty and must be repaired.
a. Connect the poc ...
Other materials:
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.
b. Connect the pocket tester ( × 1)
to the diode
terminals as shown.
c. Check the diod ...
Installing the cylinder head
1. Install:
Cylinder head
NOTE:
Pass the timing chain through the timing chain
cavity.
2. Tighten:
Cylinder head bolts "1"
Cylinder head bolts "2"
NOTE:
Lubricate the cylinder head bolts and washers
with engine oil.
Tighten the cylinder head bolts in the proper
tighten ...
Checking the clutch housing
1. Check:
Clutch housing dogs "1"
Damage/pitting/wear
Deburr the clutch
housing dogs or replace the clutch housing.
NOTE:
Pitting on the clutch housing dogs will cause erratic
clutch operation.
2. Check:
Bearing
Damage/wear Replace the
bearing and
clutch housin ...