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:
Rider seat
To remove the rider seat
Insert the key into the seat lock,
and then turn it clockwise.
Seat lock
Open.
Pull the rider seat off.
To install the rider seat
1. Insert the projection on the front of
the rider seat into the seat holder
as shown.
Projection
...
General tightening torque specifications
This chart specifies tightening torques for standard
fasteners with a standard ISO thread pitch.
Tightening torque specifications for special components
or assemblies are provided for each
chapter of this manual. To avoid warpage, tighten
multi-fastener assemblies in a crisscross pattern
and ...
Removing the piston
1. Remove:
Piston pin clips "1"
Piston pin "2"
Piston "3"
CAUTION:Do not use a hammer to drive the piston
pin
out.
NOTE:
Before removing the piston pin clip, cover the
crankcase opening with a clean rag to prevent
the piston pin clip from falling in ...