Yamaha YZF-R125 Service Manual: Installing the cylinder head
1. Install:
- Cylinder head
NOTE:
Pass the timing chain through the timing chain cavity.
2. Tighten:
- Cylinder head bolts "1"
- Cylinder head bolts "2"
NOTE:
- Lubricate the cylinder head bolts and washers with engine oil.
- Tighten the cylinder head bolts in the proper tightening sequence as shown and torque them in two stages.
3. Install:
- Camshaft sprocket
a. Turn the crankshaft counterclockwise.
b. Align the "I" mark "a" on the generator rotor with the stationary pointer "b" on the generator cover.
c. Align the "I" mark "c" on the camshaft sprocket with the stationary pointer "d" on the cylinder head.
d. Install the timing chain onto the camshaft sprocket, and then install the camshaft sprocket onto the camshaft.
NOTE:
When installing the camshaft sprocket, be sure to keep the timing chain as tight as possible on the exhaust side.
| CAUTION: Do not turn the crankshaft when installing the camshaft(s) to avoid damage or improper valve timing. |
e. While holding the camshaft, temporarily tighten the camshaft sprocket bolt.
f. Remove the wire from the timing chain.
4. Install:
- Timing chain tensioner gasket
- Timing chain tensioner
a. Apply sealant to the timing chain tensioner
bolt threads. 
b. While lightly pressing the timing chain tensioner rod by hand, turn the tensioner rod fully clockwise with a thin screwdriver "1".
c. With the timing chain tensioner rod turned all the way into the timing chain tensioner housing (with the thin screwdriver still installed), install the gasket and the timing chain tensioner "2" onto the cylinder block.
d. Tighten the timing chain tensioner bolts "3" to
the specified torque. 
e. Remove the screwdriver, make sure the timing chain tensioner rod releases.
5. Turn:
- Crankshaft (several turns counterclockwise)
6. Check:
- "I" mark "a" Align the "I" mark on the generator rotor with the stationary pointer "b" on the generator cover.
- "I" mark "c"
Align the "I" mark on the camshaft sprocket
with the stationary pointer "d" on the cylinder
head.
Out of alignment
Correct.Refer to the installation steps above.
7. Tighten:
- Camshaft sprocket bolt
| CAUTION: Be sure to tighten the camshaft sprocket bolt to the specified torque to avoid the possibility of the bolt coming loose and damaging the engine. |
8. Measure:
Valve clearance
Out of specification 
Adjust.
Refer to "ADJUSTING THE VALVE CLEARANCE" on page 3-3.
Checking the decompression system
1. Check:
Decompression system
a. Check the decompression system with the
camshaft sprocket and the decompression
cam installed to the camshaft.
b. Check that the decompression lever "1"
...
Camshaft
...
Other materials:
Ignition circuit cut-off system
The ignition circuit cut-off system (comprising
the sidestand switch, clutch
switch and neutral switch) has the following
functions.
It prevents starting when the transmission
is in gear and the sidestand
is up, but the clutch lever is
not pulled.
It prevents starting when the t ...
Removing the front fork legs
The following procedure applies to both of the
front fork legs.
1. Stand the vehicle on a level surface.
WARNINGSecurely support the vehicle so that there
is
no danger of it falling over.
2. Loosen:
Handlebar pinch bolt "1"
Handlebar bolt "2"
Upper bracket ...
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 ...