Yamaha YZF-R125 Service Manual: Checking the ignition timing
NOTE:
Prior to checking the ignition timing, check the wiring connections of the entire ignition system.
Make sure all connections are tight and free of corrosion.
1. Remove:
- Rider seat
- Left lower side cowling Refer to "GENERAL CHASSIS" on page 4-1.
2. Remove:
- Timing mark accessing screw "1"
3. Lift the fuel tank. (Do not disconnect the fuel hose, fuel drain hose, and couplers.) Refer to "FUEL TANK" on page 7-1.
4. Connect:
- Timing light "1"
- Digital tachometer
5. Check:
- Ignition timing
a. Start the engine, warm it up for several minutes,
and then let it run at the specified engine
idling speed. 
b. Check that stationary pointer "a" in the generator cover is within the firing range "b" on the generator rotor.
Incorrect firing range → Check the ignition system.
NOTE:
The ignition timing is not adjustable.
6. Remove:
- Digital tachometer
- Timing light
7. Install:
- Fuel tank Refer to "FUEL TANK" on page 7-1.
8. Install:
- Timing mark accessing screw
(along with the O-ring
)
9. Install:
- Left lower side cowling
- Right side cover
- Rider seat Refer to "GENERAL CHASSIS" on page 4-1.
Checking the spark plug
1. Remove:
Right side cover
Refer to "GENERAL CHASSIS" on page 4-1.
2. Disconnect:
Spark plug cap
3. Remove:
Spark plug
CAUTION:Before removing the spark plug, blow away
...
Measuring the compression pressure
NOTE:
Insufficient compression pressure will result in a
loss of performance.
1. Measure:
Valve clearance
Out of specification →Adjust.
Refer to "ADJUSTING THE VALVE CLEARANCE"
on page ...
Other materials:
Checking the piston pin
1. Check:
Piston pin
Blue discoloration/grooves
Replace the
piston pin and then check the lubrication system.
2. Measure:
Piston pin outside diameter "a"
Out of specification Replace
the piston pin.
3. Measure:
Piston pin bore diameter "b"
Out of specifica ...
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. ...
Removing the front brake caliper
NOTE:
Before disassembling the brake caliper, drain
the brake fluid from the entire brake system.
1. Remove:
Brake hose union bolt "1"
Copper washers "2"
Brake hose "3"
NOTE:
Put the end of the brake hose into a container
and pump out the brake fluid carefully.
...