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 fuel pressure
1. Check:
Pressure regulator operation
a. Remove the fuel hose connector cover "1"
and disconnect the fuel hose "2" from the fuel
pump.
CAUTION:Although the fuel has been removed from
the fuel tank, be careful when removing the
fuel hose, since there may be fuel remaining
i ...
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 ...
Rider seat
To remove the rider seat
Insert the key into the seat lock,
and then turn it clockwise.
Seat lock
Open.
Pull the rider seat off.
To install the rider seat
1. Insert the projection on the front of
the rider seat into the seat holder
as shown.
Projection
...