Yamaha YZF-R125 Service Manual: 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 compression stroke, align the "I" mark "c" on the camshaft sprocket with the mark "d" on the cylinder head.
2. Loosen:
- Camshaft sprocket bolt "1"
NOTE:
While holding the generator rotor nut with a wrench "2", loosen the camshaft sprocket bolt.
3. Remove:
- Camshaft sprocket
NOTE:
To prevent the timing chain from falling into the crankcase, fasten it with a wire "1".
4. Remove:
- Cylinder head
NOTE:
- Loosen the bolts in the proper sequence as shown.
- Loosen each bolt 1/2 of a turn at a time. After all of the bolts are fully loosened, remove bolts 1, 2, 4, and 6, and then remove the cylinder head with bolts 3 and 5 installed in the bolt holes.
Cylinder head
* Yamaha bond No. 1215 (Three Bond No. 1215) ...
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
...
Other materials:
Intake air pressure sensor
1. Check:
Intake air pressure sensor output voltage
Out of specification Replace the throttle
body.
a. Connect the pocket tester (DC 20 V) to the
throttle body sensor assembly coupler as
shown.
Positive tester probe
pink/white "1"
Negative tester probe
gray/black "2"
...
Checking the speed sensor
1. Check:
Speed sensor output voltage
Out of specification → Replace.
a. Connect the pocket tester (DC 20 V) to the
speed sensor coupler (wire harness end) as
shown.
Positive tester probe
gray "1"
Negative tester probe
gray/black "2"
b. Set the main switch to "ON".
c. ...
Care
While the open design of a motorcycle
reveals the attractiveness of the technology,
it also makes it more vulnerable.
Rust and corrosion can develop
even if high-quality components are
used. A rusty exhaust pipe may go unnoticed
on a car, however, it detracts
from the overall appearanc ...