Yamaha YZF-R125 Service Manual: Checking the starter clutch
1. Check:
- Starter clutch rollers "1"
- Starter clutch spring caps "2"
- Starter clutch springs "3"
Damage/wear 
Replace the starter
clutch
assembly.
2. Check:
- Starter clutch idle gear
- Starter clutch gear Burrs/chips/roughness/wear Replace the defective part(s).
3. Check:
- Starter clutch gear contacting surfaces Damage/pitting/wear Replace the starter clutch gear.
4. Check:
- Starter clutch operation
a. Install the starter clutch gear "1" onto the starter clutch and hold the generator rotor.
b. When turning the starter clutch gear clockwise "A", the starter clutch and the starter clutch gear should engage, otherwise the starter clutch is faulty and must be replaced.
c. When turning the starter clutch gear counterclockwise
"B", it should turn freely, otherwise
the starter clutch is faulty and must be replaced.
Removing the starter clutch
1. Remove:
Starter clutch bolts "1"
NOTE:
While holding the generator rotor "2" with the
sheave holder "3", remove the starter clutch
bolts.
Do not allow the sheave holder to touch th ...
Installing the starter clutch
1. Install:
Starter clutch assembly
Starter clutch bolts "1"
NOTE:
While holding the generator rotor "2" with the
sheave holder "3", tighten the starter clutch
bolts.
Do not allow t ...
Other materials:
Adjusting the throttle cable free play
NOTE:
Prior to adjusting the throttle cable free play, the
engine idling speed should be adjusted.
1. Check:
Throttle cable free play "a"
Out of specification →Adjust.
2. Remove:
Right side panel
Refer to "GENERAL CHASSIS" on page 4-1.
3. Adjust:
Throttle cable f ...
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
any dirt accumulated in the spark plug well
with compressed air to prevent it from falling
...
Adjusting the drive chain slack
NOTE:
The drive chain slack must be checked at the
tightest point on the chain.
CAUTION:A drive chain that is too tight will
overload
the engine and other vital parts, and one that
is too loose can skip and damage the swingarm
or cause an accident. Therefore, keep
the drive ...