Yamaha F400A 2022 - Checking the Cylinder Head Bolt; Checking the Valve Spring

7-60
Cylinder head
TIP:
Check the cylinder head warpage using a
straightedge “1” and a thickness gauge “2” in
6 directions.
Checking the cylinder head bolt
1. Measure:
• Cylinder head bolt diameter
Above specification → Replace.
TIP:
Measure the diameters “a” and “b” of the cyl-
inder head bolt (M11) at the specified measur-
ing points “c” and “d”.
Checking the valve spring
1. Measure:
• Free length “a”
Below specification → Replace.
2. Measure:
• Spring tilt “a”
Above specification → Replace.
Warpage limit
0.10 mm (0.0039 in)
1
2
d
ba
c
Cylinder head bolt (M11) diameter
difference limit
“a” – “b” = Less than 0.20 mm
(0.0079 in)
Measuring point “c”: 10.0 mm
(0.39 in)
Measuring point “d”: 85.0 mm
(3.35 in)
Free length IN
48.08 mm (1.89 in)
Limit
45.68 mm (1.80 in)
Free length EX
48.08 mm (1.89 in)
Limit
45.68 mm (1.80 in)
a
a