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 crankshaft position sensor
1. Disconnect:
Crankshaft position sensor coupler
(from the wire harness)
2. Check:
Crankshaft position sensor resistance
Out of specification Replace
the crankshaft
position sensor/stator assembly.
a. Connect the pocket tester ( × 100) to the
crankshaft position sensor c ...
Cleaning the air filter element
NOTE:
There is a check hose "1" at the bottom of the air
filter case. If dust and/or water collects in this
hose, clean the air filter element and air filter
case.
1. Remove:
Rider seat
Refer to "GENERAL CHASSIS" on page 4-1.
2. Remove:
Fuel tank
Refer to "FUEL TANK" on page ...
Checking the valve springs
The following procedure applies to all of the
valve springs.
1. Measure:
Valve spring free length "a"
Out of specification Replace the valve
spring.
2. Measure:
Compressed valve spring force "a"
Out of specification Replace the valve
spring.
b. Installed length
3. ...