Yamaha XS650SE, Shop Manual, Page: 29 / 215

c. Another symptom of a fatigued spring is
insufficient spring pressure when com-
pressed. This can be checked using a valve
spring compression rate gauge. Test each
spring individually. Place it in the gauge
and compress the spring first to the
specified compressed length with the valve
closed (all spring specifications can be
found in the previous section, valve
spring), then to length with the valve
open. Note the poundage indicated on the
scale at each setting. Use this procedure
with outer springs, then the inner spring.
NOTE:
All valve springs must be installed with
greater pitch upward as shown.
Larger patch
2. Smaller
d. Valve spring specifications
Compressed 53.5 61.5 kg 25.5 29.0 kg
E. Rocker arm and rocker shaft.
1. The rocker arm usually wears at two
locations: (1) at the rocker shaft hole, (2)
at the cam lobe contacting surface.
2. Measure the rocker shaft hole in the
rocker arm.
Standard size:
15.000 ~ 15.018 mm
(0.5906 ~ 0.5913 in)
3. The shaft has been hardened and it should
not wear excessively. If a groove has
developed in this surface that can be felt,
or if it shows a blue discoloration, then
the shaft should be replaced and the
lubrication system (pump and passages)
checked.
Standard shaft diameter:
14.985 ~ 14.991 mm
(0.5900 ~ 0.5902 in)
rocker
4. Standard clearance between the
shaft and hole should be 0.009 ~ 0.033
mm (0.00035 ~ 0.00130 in). If measure-
ment shows more than 0.1 mm (0.0004
in) clearance, replace either or both parts
as necessary.
F. Camshaft wear
1.
2.
3.
The cam lobe metal surface may have a
blue discoloration due to excessive fric-
tion. The metal surface could also start to
flake off or become pitted. This is due to
poor lubrication, incorrect clearances
(from poor adjustment or valve bounce),
or due to normal wear.
If any of the above wear conditions are
readily visible, the camshaft should be re-
placed. Also, the corresponding rocker
arm contacting surface should be checked
for similar wear and replaced if obvious
wear is noted.
Even though the cam lobe surface appears
to be in satisfactory condition, the lobes
should be measured with a micrometer.
Cam lobe wear can occur without scarring
the surface. If this wear exceeds a pre-
determined amount, valve timing and lift
are affected. Replace the camshaft if wear
exceeds the limits listed below.
Cam
Width
Standard Value
Wear
Standard Value
Wear
Intake
mm 84 mm
mm 32.09 mm
269f0.002
(1.263
40 mm 139.88 mm mm
32.15 mm
002 (1.266 in)
25