Yamaha YZF-R125 Service Manual: Removing the valves
The following procedure applies to all of the valves and related components.
NOTE:
Before removing the internal parts of the cylinder head (e.g., valves, valve springs, valve seats), make sure the valves properly seal.
1. Check:
- Valve sealing
Leakage at the valve seat
Check
the valve face, valve seat, and valve seat width.Refer to "CHECKING THE VALVE SEATS" on page 5-20.
a. Pour a clean solvent "a" into the intake and exhaust ports.
b. Check that the valves properly seal.
NOTE:
There should be no leakage at the valve seat "1".
2. Remove:
- Valve cotters "1"
NOTE:
Remove the valve cotters by compressing the
valve spring with the valve spring compressor
and the valve spring compressor attachment "2".
3. Remove:
- Upper spring seat "1"
- Valve spring "2"
- Valve "3"
- Valve stem seal "4"
- Lower spring seat "5"
NOTE:
Identify the position of each part very carefully so that it can be reinstalled in its original place.
Checking the valves and valve guides
The following procedure applies to all of the
valves and valve guides.
1. Measure:
Valve-stem-to-valve-guide clearance
Out of specification Replace the
valve
guide.
Valve-stem-to-valve ...
Other materials:
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 pocket tester (DC 20 V) to the
turn signal relay terminal as shown.
- Positive tester probe
b ...
Checking the cylinder and piston
1. Check:
Piston wall
Cylinder wall
Vertical scratches Replace the
cylinder,
and replace the piston and piston rings as a
set.
2. Measure:
Piston-to-cylinder clearance
a. Measure cylinder bore "C" with the cylinder
bore gauge.
NOTE:
Measure cylinder bore "C" by takin ...
Adjusting the clutch cable free play
1. Check:
Clutch cable free play "a"
Out of specification Adjust.
2. Adjust:
Clutch cable free play
a. Pull back the rubber cover "1"
b. Loosen the locknut "2".
c. Turn the adjusting bolt "3" in direction "a" or
"b" until the specified clutch cable free play is
obtained.
...