Rocker Arms And Rocker Arm Shafts; Valve Installation - Yamaha XT550J Service Manual

2. Another symptom of spring fatigue is in -
sufficient spring pressure. This can be
checked with a valve-spring-compres-
sion-rate gauge. Test each spring in-
dividually. Place a spring in the gauge
and note the spring pressure when the
spring is compressed to the installed
length (valve closed). If the pressure
does not equal the specified value,
replace the spring.
Valve Spring Specifications
--------
Outer Spring
Inner Spring
Free length
43.8mm 40.1 mm
(1.72 in)
(1.58 in)
Installed length
34.2mm 31.2mm
(valve closed)
(1.346in) (1.228in)
Installed pressure 16.0 kg
8.1 kg
(valve closed)
(37.3Ib) (17.9Ib)
Allowable tilt
2.5
0
2.5
0
from vertical (1.9mm)
(1.7mm)
Valve installation
RETAINERS----___.
COLLAR
1. Lubricate the valve stem and the oil seal
with a high-quality molybdenum
disulfide motor oil or molybdenum
disulfide grease.
2. Insert the valve in the cylinder head, and
install the oil seal. Carefully fit the oil
seal over the valve stem and push it into
position on top ofthe valve guide.
3. Install the spring seat, and install both
valve springs.
3-17
NOTE: _ _ _ _ _ _ _ _ _ _ _ _
All valve springs must be installed with the
larger pitch upward as shown.
LARGER PITCH
o~
0>
o
o
o
O~SMALLER
PITCH
'>
4.
Install the collar. Be sure it is properly
seated on the valve springs.
5. Install the valve spring compressor, and
compress the springs.
6.
Install the valve retainers. Be sure the re-
tainers properly engage the valve stem.
7. Carefully remove the valve spring com-
pressor.
WARNING:
Proceed slowly. If a retainer has not
been properly installed, it could be
ejected from the cylinder head.
8. Gently tap the end of the valve stem
with a plastic mallet. This will ensure
that the retainers are properly seated in
the collar.
D. Rocker Arms and Rocker Arm
Shafts
1.
The rocker arm usually wears at two
locations: at the rocker shaft hole and at
the cam-lobe-contact surface. Check
these areas for signs of unusual wear.
2. Measure the rocker arm inside diameter.
If it exceeds specification, replace the
rocker arm.
Maximum inside diameter:
12.05 mm (0.474 in)