Yamaha YZF-R125 Service Manual: Checking the cylinder head
1. Eliminate:
- Combustion chamber carbon deposits (with a rounded scraper)
NOTE:
Do not use a sharp instrument to avoid damaging or scratching:
- Spark plug bore threads
- Valve seats
2. Check:
- Cylinder head
Damage/scratches
Replace. - Cylinder head water jacket
Mineral deposits/rust
Eliminate.
3. Measure:
- Cylinder head warpage
Out of specification
Resurface
the cylinder head.
a. Place a straightedge "1" and a thickness gauge "2" across the cylinder head.
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylinder head as follows.
d. Place a 400-600 grit wet sandpaper on the surface plate and resurface the cylinder head using a figure-eight sanding pattern.
NOTE:
To ensure an even surface, rotate the cylinder head several times.
Removing the cylinder head
1. Align:
"I" mark "a" on the generator rotor
(with the stationary pointer "b" on the generator
cover)
a. Turn the crankshaft counterclockwise.
b. When the piston is at TDC on the compre ...
Checking the camshaft sprocket and timing chain guide
1. Check:
Camshaft sprocket
More than 1/4 tooth wear "a" Replace
the
camshaft sprocket, timing chain and crankshaft
as a set.
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. C ...
Other materials:
Checking the clutch boss
1. Check:
Clutch boss splines
Damage/pitting/wear Replace the
clutch
boss.
NOTE:
Pitting on the clutch boss splines will cause erratic
clutch operation.
Checking the pressure plate
1. Check:
Pressure plate
Cracks/damage Replace.
Checking the clutch push lever and short clutch push ...
Checking the connections
Check the leads, couplers, and connectors for
stains, rust, moisture, etc.
1. Disconnect:
Lead
Coupler
Connector
2. Check:
Lead
Coupler
Connector
Moisture → Dry with an air blower.
Rust/stains → Connect and disconnect several
times.
3. Check:
All co ...
General information
NOTICEThis manual was produced by MBK Industrie.
primarily for use by Yamaha dealers and their qualified
mechanics. It is not possible to include all the knowledge of a mechanic
in one manual. Therefore, anyone
who uses this book to perform maintenance and repairs on Yamaha vehi ...