Yamaha RS90K, Service Manual

Page: 56 / 841

2-8
INSP
ADJ
VALVE CLEARANCE ADJUSTMENT
4. Remove:
• Cylinder head cover
Refer to “CAMSHAFTS” in CHAPTER 5.
• Timing mark accessing screw
1
• Crankshaft end accessing screw 2
1
2
5. Measure:
• Valve clearance
Out of specification
→
Adjust.
Checking steps:
• Turn the crankshaft clockwise.
• When piston #3 is at TDC on the compression
stroke, align the TDC mark
a
on the A.C. mag-
neto rotor with the mark
b
on the A.C. magneto
cover.
NOTE:
TDC on the compression stroke can be found when
the camshaft lobes are turned away from each
other.
• Measure the valve clearance with a thickness
gauge
1
.
NOTE:
• If the valve clearance is incorrect, record the
measured reading.
• Measure the valve clearance in the following
sequence.
Valve clearance (cold):
Intake valve:
0.15 ~ 0.22 mm
(0.0059 ~ 0.0087 in)
Exhaust valve:
0.21 ~ 0.25 mm
(0.0083 ~ 0.0098 in)
Valve clearance measuring sequence
Cylinder #3
→
#2
→
#1
a
b
1