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:
Bleeding the hydraulic brake system
WARNINGBleed the hydraulic brake system whenever:
the system is disassembled.
a brake hose is loosened, disconnected or
replaced.
the brake fluid level is very low.
brake operation is faulty.
NOTE:
Be careful not to spill any brake fluid or allow
th ...
Checking the ignition timing
NOTE:
Prior to checking the ignition timing, check the
wiring connections of the entire ignition system.
Make sure all connections are tight and free of
corrosion.
1. Remove:
Rider seat
Left lower side cowling
Refer to "GENERAL CHASSIS" on page 4-1.
2. Remove:
Timing mark acces ...
Be a Responsible Owner
As the vehicle's owner, you are responsible
for the safe and proper operation
of your motorcycle.
Motorcycles are single-track vehicles.
Their safe use and operation are dependent
upon the use of proper riding
techniques as well as the expertise of
the operator. Every operator should
...