Yamaha F2.5C, Service Manual

Page: 90 / 184

POWR
Power unit
5-29
6D55F11
Checking the camshaft
1. Measure the cam lobe. Replace if out of
specification.
2. Measure the camshaft runout. Replace if
above specification.
3. Measure the camshaft journal diameters
c
and
d
, and cylinder head journal
inside diameter
e
. Replace the camshaft
and cylinder head if out of specification.
4. Calculate the camshaft journal oil clear-
ance as follows. Replace the camshaft
and cylinder head as a set if out of speci-
fication.
5. Check the decompression actuator for
damage or wear. Replace the camshaft if
necessary.
Checking the cylinder head
1. Eliminate carbon deposits from the com-
bustion chambers and check for deterio-
ration.
2. Check the cylinder head warpage using a
straightedge
1
and thickness gauge
2
in six directions as shown. Replace if
above specification.
Cam lobe
a
:
Intake and exhaust:
30.834–31.034 mm
(1.2139–1.2218 in)
Cam lobe
b
:
Intake and exhaust:
25.90–26.10 mm
(1.0197–1.0276 in)
Camshaft runout limit:
0.03 mm (0.0012 in)
Camshaft journal diameter
c
:
36.925–36.945 mm
(1.4537–1.4545 in)
Camshaft journal diameter
d
:
36.935–36.955 mm
(1.4541–1.4549 in)
Cylinder head journal inside
diameter
e
:
37.000–37.025 mm
(1.4567–1.4577 in)
Camshaft journal oil clearance =
Cylinder head journal inside
diameter
e
– Camshaft journal
diameter
c
,
d
:
0.050–0.090 mm
(0.0020–0.0035 in)